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UNIVERSITY  OF  ILLINOIS 


Agricultural  Experiment  Station 


BULLETIN  No.  104 


BY  S.  A.  FORBES 
STATE  ENTOMOLOGIST. 


URBANA,  OCTOBER,  1905 


CONTENTS  OF  BULLETIN  No.  104. 

1.  Injury  to  corn  by  the  timothy  bill-bugs Page    95 

Summary  of  article Page  101 

2.  Field  experiments  on  the  corn  root-aphis Page  102 

General  discussion  of  results Page  ]  20 

3.  Field  experiments  for  the  protection  of  corn  against  chinch- 

bug  injury Page  124 

Barrier  experiments Page  124 

Experiment  of  1895 , Page  124 

Experiments  of  1904 Page  125 

Carbondale  experiment Page  127 

Preparation  of  the  dusty  furrow Page  1 30 

Preparation  of  the  coal-tar  line Page  131 

Dubois  and  Odin  experiments Page  133 

Experiments  with  fluid  insecticides Page  134 

Experiments  with  the  gasoline  blast-lamp Page  137 


INJURY  TO  CORN  BY  THE  TIMOTHY  BILL-BUGS 
(SPHHNOPHORUS  SP.). 

In  a  general  article  on  "The  Corn  Bill-bugs  in  Illinois,"  pub- 
lished in  my  Eleventh  Report  as  State  Entomologist  (pages  1-26),  a 
brief  account  was  given  of  observations  made  in  fields  near  Taylor- 
ville, Christian  county,  in  1902  (page  7)  ;  but  the  data  in  my  pos- 
session concerning  injuries  to  corn  at  this  place  and  their  relation 
to  previous  crops  and  to  the  history  of  the  land,  were  not  fully  util- 
ized in  that  paper.  Our  observations  and  correspondence  have  made 
it  evident  for  some  time  that  bill-bug  injury  to  corn  is  imperfectly 
appreciated  by  corn  growers  and  but  little  understood  by  them,  and 
it  Consequently  seems  desirable  that  the  careful  work  done  on  this 
insect  injury  near  Taylorville  should  now  be  fully  reported  and  thor- 
oughly discussed. 

June  26,  1902,  Mr.  D.  S.  Dalbey,  a  senior  agricultural  student  in 
the  University  of  Illinois,  sent  me  the  following  note : — 

"I  have  received  from  my  father,  Wm.  M.  Dalbey,  of  Taylorville,  Illinois, 
some  specimens  of  corn  plants  affected  by  the  corn  bill-bug.  The  land  on  which 
the  infested  corn  was  grown  is  timothy  sod  plowed  in  April  of  this  year,  and  is 
located  two  miles  northeast  of  Taylorville,  on  my  father's  farm.  The  damaged 
area  covers  forty  acres,  and  the  extent  of  the  damage  involves  about  half  the 
stand.  The  plants  affected  are  not  dead,  but  have  a  sickly  yellow  color,  and  the 
leaves  are  punctured  with  holes." 

I  further  learned  that  this  land  had  been  in  timothy  for  the  four 
years  preceding,  and  the  year  before  that  in  wheat.  Clover  and 
timothy  had  been  originally  sown  together,  but  the  clover  ran  out 
and  the  crop  was  practically  pure  timothy  by  1901. 

EXAMINATION  OF  INJURED  FIELD. 

June  30,  1902,  I  sent  Mr.  E.  S.  G.  Titus  to  Taylorville  with  in- 
structions to  make  a  careful  study  of  the  condition  of  the  infested 
field  and  to  collect  information  for  a  comparison  of  its  agricultural 
history  with  that  of  other  fields  of  corn  in  its  neighborhood,  the  ob- 
ject being  to  ascertain  the  full  effect  of  bill-bug  injury  to  corn  on  up- 
lands, and  to  discover  any  differences  in  respect  to  this  injury  due 
to  differences  of  agricultural  management. 

This  work  was  done  by  Mr.  Titus  with  characteristic  thorough- 
ness, intelligence,  and  skill.  On  his  first  visit,  made  June  30,  he 
platted  the  Dalbey  field,  selecting  and  marking  650  hills  which  had 
been  more  or  less  injured  by  corn  bill-bugs.  On  another  visit,  August 
10  and  n,  he  made  notes  on  the  condition  of  these  hills,  and 


96  BULLETIN  No.  104.  [October, 

October  2  and  3  he  carefully  examined  them  with  reference  to  the 
condition  of  the  stalks  and  the  number  and  quality  of  the  ears,  in 
comparison  with  like  facts  concerning  uninjured  hills  in  the  same 
field.  Observations  were  also  made  on  the  condition  of  fields  of 
corn  on  other  farms  of  the  neighborhood.  The  data  thus  obtained 
have  since  been  summarized  and  tabulated  for  comparative  study, 
and  the  materials  are  thus  in  hand  for  a  fuller  study  of  Sphenoph- 
orus  injury  to  this  crop  than  has  ever  before  been  reported. 

DISTRIBUTION  OF  INJURY. 

The  injury  to  the  corn  in  the  Dalbey  field  was  very  uneven.  In 
one  corner  almost  every  stalk  on  several  acres  had  been  damaged, 
while  in  other  parts  from  25  to  50  per  cent,  of  the  plants  had  been 
attacked.  The  distribution  of  the  injury  seemed  not  affected  by  the 
lay  of  the  land  or  the  moisture  in  the  soil,  there  being  more  injury 
on  low  moist  ground  at  one  side  of  the  field  and  less  on  similar 
ground  at  the  other  side  than  there  was  on  the  higher  and  drier 
ground. 

THE  INJURIOUS  SPECIES. 

The  species  of  Sphenophorus  actually  responsible  for  this  mis- 
chief was  not  definitely  ascertained,  the  beetles  having  all  disap- 
peared from  the  field;  but  as  the  larva  of  Sphenophorus  parvulus 
was  common  in  the  bulbous  roots  of  timothy  on  adjacent  prem- 
ises, and  as  the  old  timothy  bulbs  still  present  in  the  injured 
corn  field  had  been  similarly  hollowed  out  by  bill-bug  larvae  the  year 
before,  the  probability  is  strong  that  this  species  was  largely  con- 
cerned in  the  injury  under  observation. 

THE  INJURY  TO  TIMOTHY. 

Fields  of  timothy  near  by,  which  had  been  in  that  crop  for  three 
or  four  years  in  succession,  had  at  this  time  from  50  to  75  per  cent, 
of  the  bulbs  more  or  less  injured  and  infested,  many  of  them  con- 
taining larvae  ranging  in  size  from  those  evidently  but  just  hatched 
to  those  large  enough  to  fill  the  whole  timothy"  bulb.  In  fields  but 
two  years  in  timothy,  on  the  other  hand,  from  10  to  20  per  cent,  of 
the  bulbs  were  infested.  The  injured  plants  were  inclined  to  throw 
out  suckers  at  the  base  and  also  at  the  first  joint  above  the  ground. 
Where  the  bill-bug  larva  had  eaten  out  all  the  substance  of  the  bulb, 
it  had  often  drilled  into  an  adjacent  bulb,  and  was  found  feeding 
therein.  Some  larvae  were  seen  just  cutting  their  way  out  of  the 
first  bulb,  and  others  in  the  act  of  boring  into  the  second,  a  part  of 


1905.}  EXPERIMENTS  ON  CORN  INSECTS.  97 

the  body  in  each.  The  effect  of  this  amount  of  infestation  on  the 
timothy  crop  itself  must  certainly  have  been  considerable,  and  the 
conditions  were,  of  course,  unusually  dangerous  to  the  corn  crop  fol- 
lowing. 

THE  INJURY  TO  CORN. 

The  injury  to  corn  had  resulted  variously,  the  differences  being 
probably  due  to  the  age  of  the  plant  when  injured,  and  to  the  num- 
ber of  punctures  made  in  a  single  stalk.  In  many  cases,  as  will  be 
presently  shown,  the  stalk  had  been  killed,  doubtless  when  the  plant 
was  still  quite  young.  In  other  cases  the  stalk,  though  nearly  or 
quite  full  grown,  had  fallen  to  the  ground  in  consequence  of  a  de- 
ficient root  development,  brace-roots  being  indeed  practically  lack- 
ing. Injured  stalks  were  also  smaller  than  normal  just  above  the 
ground  and  at  the  joints  higher  up,  and  were  likely  to  lean  from  the 
base  or  to  bend  at  the  weakened  joints.  A  considerable  percentage 
of  the  stalks  in  hills  which  had  been  infested  had  never  formed  the 
ear  (at  least  33  per  cent,  of  these  stalks  being  barren,  as  against  4 
per  cent  in  uninfested  hills),  and  on  a  much  larger  percentage  of 
them  the  ear  was  either  a  small  nubbin  or  imperfectly  rilled  out.  It 
was  the  owner's  opinion  that  the  worst-infested  parts  of  the  field 
averaged  about  twenty  bushels  of  corn  to  the  acre,  and  that  the  part 
not  infested  yielded  from  forty-five  to  fifty-five  bushels.* 

*A  letter  received  from  Mr.  H.  L.  Jones,  of  Geneva,  111.,  since  this  manuscript  was  pre- 
pared, makes  mention  of  an  effect  of  bill-bug'  infestation  which  has  not  previously  been  noticed, 
and  describes  also  his  method  of  diminishing  the  damage.  He  says:  "I  had  a  rather  expen- 
sive experience  with  bill-bugs  last  season  on  a  pasture  plowed  in  spring1.  They  appeared  when 
the  corn  was  four  to  six  inches  high,  and  crippled  it  badly  in  spots  so  that  the  injured  inner 
leaf  would  break  over  and  curl  up,  thereby  preventing-  the  next  inner  leaf  from  coming-  out 
and  thus  dwarfing  the  stalk.  I  immediately  put  men  and  boys  into  the  field,  who  replanted 
the  destroyed  hills  and  picked  the  curled  tops  from  all  the  damaged  stalks,  in  this  way  saving 
nearly  all  the  crop.  This  corn  busked  seventy  bushels  per  acre  where  I  am  sure  that  it  would 
have  yielded  eiifhty  bushels  but  for  the  damage  sustained.  If  the  curled  leaves  had  not  been 
picked  from  the  tops  of  the  plants,  I  think  that  the  crop  would  not  have  been  more  than  fifty 
bushels.  The  labor  cost  about  $5.00  for  twelve  acres,  and  it  might  help  some  other  man  to 
know  my  experience  in  saving  part  of  a  crop." 

GENERAL,  RESULTS  01?  THE  INJURY. 

As  affecting  the  whole  Plant. — For  a  precise  comparison  of  the 
condition  of  uninjured  corn  with  that  of  corn  attacked  by  the  bill- 
bugs,  328  hills  were  carefully  selected  as  representing  the  average 
condition  of  infested  and  uninfested  hills  in  this  field.  One  hun- 
dred and  sixty-four  of  these  were  free  from  injury,  and  each  of 
the  remaining  164  contained  injured  stalks.  There  were,  in  all,  363 
stalks  in  the  uninjured  hills  and  313  in  the  injured  hills, — a  differ- 
ence indicating  that  50  stalks,  or  14  per  cent,  of  the  whole,  had  been 
killed  by  the  bill-bugs.  In  the  uninjured  hills  306  stalks  were  stand- 
ing erect,  29  were  leaning,  and  28  had  fallen  to  the  ground.  In  the 
injured  hills  64  stalks  were  standing,  99  were  leaning,  and  150  had 


98  BULLETIN  No.  104.  [October, 

fallen.  That  is,  33  per  cent,  of  the  number  of  the  stalks  which 
should  have  been  erect  in  the  injured  hills  had  been  made  to  fall,  and 
19  per  cent,  of  them  had  been  weakened  sufficiently  to  cause  them  to 
lean  or  bend.  More  generally  speaking,  67  per  cent,  of  the  stalks — 
that  is,  242  out  of  363 — had  been  either  killed  or  noticeably  injured 
in  the  infested  hills. 

The  ratio  of  damage  to  the  plant  as  a  whole  may  be  more  simply 
and  forcibly  shown  by  saying  that  in  the  uninjured  hills  there  were 
306  stalks  erect  and  in  good  condition,  while  in  the  injured  hills 
there  were  but  64  such  stalks.  In  other  words,  the  bill-bugs  had 
killed  or  palpably  damaged  79  per  cent,  of  the  stalks  in  the  infested 
hills  which  would  have  continued  in  good  condition  except  for  this 
insect  attack. 

As  affecting  the  Ears. — Comparing  the  two  lots  with  reference  to 
the  number  and  condition  of  the  ears  borne  by  them  respectively,  we 
find  that  the  uninjured  hills  bore  349  ears  of  all  kinds,  and  the  in- 
jured hills  211, — a  loss  of  138  ears,  or  40  per  cent,  of  the  whole.  Of 
the  uninjured  corn  282  of  the  ears  were  graded  as  good,  44  as  fair, 
14  as  poor,  and  9  as  nubbins,  while  the  injured  corn  bore  24  good 
ears,  75  fair  ears,  72  poor  ones,  and  40  nubbins.*  (See  Fig.  i.) 
Otherwise  stated,  besides  the  40  per  cent,  of  the  ears  which  had  been 
sacrificed  to  the  bill-bugs,  9  per  cent,  had  been  considerably  injured 
and  26  per  cent,  had  been  badly  injured  as  a  result  of  bill-bug  at- 
tack. Not  less  than  75  per  cent,  of  the  ears  in  these  hills  were  thus 
either  lost  or  seriously  injured. 

The  loss  in  number  and  condition  of  the  ears  borne  by  infested 
hills  may  perhaps  be  more  clearly  illustrated  by  the  statement  that 
282  good  ears  were  borne  by  the  uninjured  hills  and  only  24  by  the 
injured, — a  loss  and  injury  combined  amounting  to  81  per  cent. 

It  further  appears  from  the  data  in  hand  that  the  uninjured  hills 
bore  96  ears  per  hundred  stalks,  and  the  injured  hills  67  ears  per 
hundred, — a  loss  of  thirty  per  cent,  in  number  of  ears  per  hundred 
stalks, — and  that  the  uninjured  corn  yielded  an  average  of  200  good 
or  fair  ears  per  hundred  hills,  and  the  injured  corn  73  such  ears  per 
hundred  hills, — a  loss  of  61  per  cent,  in  number  of  fairly  good  ears. 

TOTAL  AMOUNT  OF  INJURY. 

The  above  ratios  do  not  hold,  of  course,  for  the  entire  field,  but 
only  for  the  part  injured,  and  for  an  understanding  of  the  condition 
of  the  field  in  general  an  estimate  of  the  percentage  of  injured  hills 
is  necessary.  Six  hundred  and  eighty-two  hills  were  examined  for 


*"Fair  ears"  were  of  medium  size   and    imperfectly   filled,  "poor  ears"   were   short   and 
ly  filled,  and  nubbins  were  short, 
ormed,  with  poor  and  injured  grain. 


poorly  filled,  and  nubbins  were  short,  small,  and  not  filled  to  the  tip,  and  were  otherwise  de- 
f<          '       '  ' 


1905.'] 


EXPERIMENTS  ON  CORN  INSECTS. 


this  purpose,  and  199,  or  29  per  cent.,  were  found  injured;  from 
which  we  learn  by  a  simple  computation  that  approximately  12  per 
cent,  of  the  ears  which  the  entire  field  should  have  yielded  were  lost 
in  consequence  of  bill-bug  injury,  and  that  7  per  cent,  were  badly 
injured  and  3  per  cent,  considerably  so. 


Fig-.  1.    Sample  Ears  from  Dalbey  field;    "g-ood.^'  "fair,"  and  "poor''  grades  of  this  paper,  i 

Samples  of  uninjured  ears  and  of  those  called  badly  injured, 
brought  in  by  Mr.  Titus,  indicate  that  the  yield  from  "fair  ears," 
"poor  ears,"  and  nubbins  would  not  be  more  than  one  third  of  that 
from  an  equal  number  of  ears  of  the  uninjured  corn.  It  is  proper  to 
add,  consequently,  to  the  12  per  cent,  of  total  loss  some  two  thirds 
of  the  10  per  cent,  of  injured  ears,  making  another  6  per  cent,  of 
loss,  or  a  total  of  18  per  cent,  for  the  entire  field. 

This  conclusion  is  substantially  supported  by  the  owner's  esti- 
mate of  twenty  bushels  per  acre  for  the  infested  area  and  fifty 
bushels  for  the  uninfested;  since,  by  using  the  above-mentioned 
ratio  of  29  per  cent,  for  the  number  of  hills  injured,  we  find  that  the 
average  yield  would  be  41.3  bushels  per  acre,  a  quantity  loss  of  8.7 
bushels  per  acre  because  of  bill-bug  injury,  or  17  per  cent,  of  the 
normal  yield.  No  account  is  taken  in  this  estimate  of  the  deteriora- 
tion in  quality  of  the  injured  corn,  which,  if  included,  would  increase 
the  loss  materially.  As  the  season  was  a  favorable  one  for  corn,  and 
as  the  variety  used  (Reid's  Yellow  Dent)  was  reported  to  have 
hardened  much  earlier  than  other  varieties  planted  at  the  same  time, 
this  loss  is  probably  under  rather  than  over  the  general  average  un- 


100 


BULLETIN  No.  10J. 


[October, 


der  similar  conditions  of  injury.     The  following  table  will  serve  to 
exhibit  these  data  and  conclusions  in  more  compact  form. 

STATISTICS  OF  BILL-BUG  INJURY  TO  CORN,  DALBEY  FIELD,  1902. 


Uninjured  hills 

Injured  hills 

Losses  from  injury 

No. 

Per  cent. 

No. 

Per  cent. 

No. 

Per  cent. 

Number  of  hills.  . 

164 

164 

Number  of  stalks 

363 

313 

86 

50 

14 

Fallen  stalks  .... 

28 

8 

150 

48 

122 

33 

Leaning  stalks  .. 

29 

8 

99 

27 

70 

19 

Erect  stalks  

306 

64 

21 

242 

79 

Number  of  ears.  . 

349 

211 

60 

138 

40 

Nubbins  

9 

3 

40 

12 

31 

9 

Poor  ears  

14 

4 

72 

21 

58 

17 

Fair  ears  

44 

13 

75 

22 

31 

9 

Good  ears  

282 

24 

9 

258 

81 

METHODS  OF  PREVENTION. 

The  contrast  observed  between  corn  grown  on  timothy  sod  and 
plowed  early  in  fall,  and  the  Dalbey  field,  which  was  plowed  only  a 
few  days  before  planting,  was  discussed  in  my  Eleventh  Report. 
No  trace  of  bill-bug  injury  was  detected  on  the  fall-plowed  land,  al- 
though dead  timothy  bulbs  still  in  the  ground  showed  distinctly 
that  they  had  been  hollowed  out  by  bill-bug  larvae.  The  inference  is 
thus  strongly  suggested  that  early  fall-plowing  of  timothy  previous 
to  corn  planting  will  protect  the  corn  from  injury.  A  similar  state- 
ment was  made  in  1892  by  Osborn  and  Gossard,  who  say  that  since 
worse  injuries  are  likely  to  occur  on  land  in  grass  the  preceding  year 
or  adjacent  to  such  land,  plowing  should  be  done  as  early  in  the  pre- 
vious season  as  possible;  and  that  since  bill-bug  injury  is  mainly 
done  early,  infested  ground  should  be  planted  as  late  as  practicable.* 

John  B.  Smith,  the  State  Entomologist  of  New  Jersey,  advised, 
in  the  same  year,  plowing  of  sod  for  corn  in  fall  and  early  winter, 
with  a  view  to  killing  out  the  bill-bug  larvae  living  in  or  under  the 
sod;  and  in  the  following  year  he  says  that  this  injury  has  been 
minimized  where  fall  plowing  has  been  practiced,  t 

F.M.  Webster  also  surmises  +  that  fall  plowing  would  probably 
result  in  the  diminution  or  prevention  of  the  injury,  and  suggests 
planting  some  other  crop  than  corn  where  the  occurrence  of  this  in- 
jury is  very  probable;  and  H.  E.  Weed  says  in  1895  £  that  where 

*Bull.  18,  la.  Agr.  Exper.  Station,  pp.  507-509. 

•(•Twelfth  and  Thirteenth  Ann.  Reports,  N.  J.  Agr.  Exper.  Station,  for  the  years  1891  (pp. 
394,  395)  and  1892  (p.  390). 

*"Ohio  Farmer,"  July  20, 1893,  p.  57. 
§Bull.  35,  Miss.  A.gr.  Exper.  S  ation,  p.  154. 


1905.}  EXPERIMENTS  ON  CORN  INSECTS.  101 

sod  has  been  broken  up  in  fall  the  bill-bugs  will  do  but  little  damage 
the  following  spring,  and  that  the  second  planting,  whenever  the 
time  of  plowing,  will  be  little  if  at  all  attacked. 

Early  fall-plowing  of  grass-lands  would  consequently  seem,  in 
the  present  state  of  our  knowledge,  to  diminish  greatly,  if  not  com- 
pletely to  prevent,  injury  to  corn  by  bill-bugs  the  following  year;  a 
statement  which  must  be  applied  to  blue-grass  pastures  as  well  as 
to  timothy  meadows,  since  the  bill-bug  most  abundant  in  timothy, 
Sphenophorus  parvulus,  has  also  been  found  destructive  in  blue- 
grass  lawns.  (See  Bull.  22,  U.  S.  Dept.  Agr.,  Div.  Ent.,  p.  99.) 

As  a  check  to  injury  to  timothy  meadows  I  see  nothing  better 
than  to  avoid  keeping  the  same  ground  in  timothy  for  more  than  two 
years  at  a  time  Where  the  pest  becomes  so  common  and  destructive 
as  in  the  Dalbey  neighborhood,  it  would  seem  wise  to  substitute 
clover  for  timothy,  so  far  as  practicable,  for  a  considerable  term  of 
years. 

SUMMARY. 

In  a  forty-acre  field  of  corn  in  Christian  county,  injury  by  bill- 
bugs  was  found  to  have  affected  about  29  per  cent,  of  the  hills,  di- 
minishing the  number  of  stalks  in  such  hills  by  14  per  cent,  and  the 
number  of  ears  by  40  per  cent.,  and  seriously  injuring  26  per  cent, 
more  of  the  ears.  It  also  caused  about  a  third  of  the  stalks  in  the 
injured  hills  to  fall  to  the  ground,  and  weakened  about  a  fifth  of 
them  additional.  The  total  loss  in  the  field  was  estimated  at  18  per 
cent,  of  the  crop,  or  nearly  nine  bushels  to  the  acre. 

Comparison  of  this  with  other  fields  shows  that  the  injury  was 
due  to  planting  corn  after  timothy  plowed  in  spring,  and  that 
most  of  it  could  have  been  prevented  by  early  fall-plowing  of  the 
timothy  sod. 


102  BULLETIN  No.  104.  \0ctober, 


FIELD  EXPERIMENTS  ON  THE  CORN  ROOT-APHIS 
(APHIS  MAIDIRADICIS  FORBES). 

The  corn  root-aphis,  wintering  as  an  egg  in  the  nests  of  ants  in 
corn  fields,  begins  to  hatch,  according  to  our  observations  in  central 
Illinois,  about  April  8,  and  may  continue  this  process  for  as  much  as 
six  weeks,  or  until  the  latter  part  of  May.*  The  earliest  individuals 
of  this  first  generation  get  their  growth  in  approximately  twenty 
days,  and  then  give  origin  at  once  to  representatives  of  the  second 
generation,  which  in  eighteen  or  nineteen  days  may  themselves  be- 
gin to  reproduce.  The  growing  period  for  an  individual  of  the  third 
generation  is  approximately  eleven  days,  making  a  total  of  not  far 
from  fifty  days  for  the  entire  life  of  a  series  of  the  first  born  of  the 
first  three  generations  from  the  egg.  That  is,  by  the  last  of  May 
the  latest  to  hatch  of  the  first  generation  would  coexist  in  the  fields 
with  the  earliest  born  of  the  third  generation.  All  hatching  from 
the  egg  are  wingless  females,  but  a  small,  and  no  doubt  variable, 
percentage  of  the  second  and  third  generations  are  winged,  and 
leave  their  underground  quarters  to  fly  abroad  and  start  new  col- 
onies elsewhere.  The  later  steps  of  this  life  history  are  not  neces- 
sary to  a  discussion  of  the  experiments  here  reported. 

In  view  of  the  fact  that  the  young  lice  are  dependent  upon  their 
attendant  ants,  at  least  until  they  have  been  placed  upon  the  roots  of 
plants  suitable  for  their  maintenance,  it  has  seemed  to  me  prob- 
able that  an  early  and  repeated  stirring  of  the  ground  infested  by 
these  insects  in  early  spring,  scattering  the  eggs  and  young  aphids 
again  and  again  through  the  dirt,  and  killing  the  young  weeds  in  the 
corn  field  upon  which  they  must  at  first  depend  for  food,  wrould 
have  the  effect  to  destroy  great  numbers  of  them  and  thus  to  weaken 
the  force  of  the  aphis  attack  upon  the  young  corn  at  a  time  when  it 
is  most  susceptible  to  injury. 

THE  SEASON  OE  1904. 

With  a  view  to  testing  this  supposition,  a  field  experiment  was 
arranged  in  the  spring  of  1904,  to  be  made  in  two  neighborhoods 
notorious  for  some  years  for  an  abundance  of  the  root-aphis  on 
corn  and  a  considerable  injury  to  the  crop  in  consequence.  Circum- 
stances beyond  my  control  prevented,  last  year,  as  early  a  beginning 
as  might  have  been  desirable,  and  nothing  was  done  in  the  experi- 

*We  have  this  year  collected  eggs  of  the  corn  root-aphis  from  ants'  nests  in  the  field  May 
19.  These  eggs  hatched  under  our  observation,  and  the  young- were  maintained  on  corn,  but 
were  not  kept  until  mature. 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  103 

mental  fields  until  May  13  in  one  locality,  and  May  23  in  the  other. 
I  owe  the  opportunity  to  undertake  the  investigation  at  this  time  to 
Dr.  J.  W.  Folsom,  Instructor  in  Entomology  at  the  University  of 
Illinois,  who  was  good  enough  to  undertake  the  field  inspections 
for  me,  and  upon  the  report  of  whose  observations  the  following 
statement  of  results  is  based. 

The  season  was  at  least  a  fortnight  later  than  usual,  and  it  is 
consequently  difficult  to  say  just  what  generations  of  the  aphis  were 
in  existence  at  the  time.  Judging,  however,  by  the  calendar  for  the 
three  earliest  generations  given  above,  and  by  the  field  and  insectary 
work  of  1905,  reported  farther  on,  it  seems  likely  that  the  first  and 
second  generations  were  abundant  in  the  fields,  and  that  the  third 
had  not  yet  begun  to  appear.  That  the  second  was  present  is  un- 
questionable, since  occasional  winged  individuals  were  found. 

The  Galesburg  Cultivation  Experiment.  (Table  I.). — In  the 
first  experiment,  made  on  the  farm  of  Mr.  J.  H.  Coolidge,  about 
three  miles  from  Galesburg,  in  Knox  county,  111.,  two  parts  of  a 
large  field  of  corn  were  used,  one  of  which  (Plat  A)  received  the 
usual  treatment  in  preparation  for  planting  and  the  ordinary  culti- 
vation afterwards,  while  in  the  other,  the  experimental  plat  (Plat, 
B),  the  ground  was  repeatedly  disked  and  harrowed  between  plow- 
ing and  planting,  and  harrowed  and  cultivated  promptly  thereafter.* 
In  this  experimental  plat  were  thirty-two  rows,  each  eighty  rods 
long,  and  in  the  check  plat  ninety  rows  of  the  same  length.  The 
latter  was  plowed  early  in  May,  planted  May  13  to  17,  harrowed 
once  thereafter,  and  cultivated  June  9,  the  condition  of  the  corn  with 
reference  to  ants  and  root-lice  being  there  determined  on  the  loth 
of  June.  The  thirty-two  experimental  rows  were  plowed  May  14 
to  1 6,  the  ground  was  thoroughly  disked  three  times  on  the  i8th, 
2 ist,  and  25th  of  May,  also  harrowed  May  25,  and  planted  on  this 
same  day.  It  was  cultivated  May  28,  harrowed  on  the  3Oth,  and 
inspected  June  10. 

It  will  be  noticed  as  an  important  difference  between  these  two 
fields  that  the  experimental  plat  was  planted  ten  days  later  than  the 

*The  various  operations  on  the  ground  used  in  these  experiments  were  as  follows:  — 
First,  plowing1  with  an  ordinary  mold-board  plow;  second,  harrowing-  with  a  toothed 
harrow;  third,  disking1  with  a  disk  harrow;  lourth,  spading  with  a  so-called  spading  harrow; 
fifth,  pulverizing' with  a  so-called  "Acme"  harrow,  sometimes  known  and  sold  as  a  "pulverizer;" 
sixth,  rolling'  with  an  ordinary  smooth  roller;  seventh,  cultivating'  with  an  ordinary  "sulky" 
cultivator  with  shovels.  These  terms  are  used  as  above  defined  throughout  this  paper  in 
both  tables  and  text.  The  plowing'  in  the  experimental  plats  was  from  five  to  seven  inches 
deep;  the  toothed  harrow  stirred  the  earth,  as  a  rule,  to  a  depth  of  about  two  inches;  the  disk 
barrow  commonly  worked  twice  as  deep  or  more,  moving1  the  dirt  laterally  and  mixing  it 
thoroughly  in  the  process;  the  spading  harrow  differed  but  little  from  the  disk  harrow  in  its 
operation  except  that  it  was  likely  to  go  deeper,  and  did  not  move  the  earth  laterally  to  so 
great  a  distance;  the ''Acme"  harrow,  or  "pulverizer,"  consisting  of  a  row  of  blades  set  ob- 
liquely into  an  angular  beam,  followed  by  a  transverse  row  of  cylindrical  pointed  teeth,  worked 
to  a  depth  of  about  three  inches,  as  a  rule,  stirring  and  pulverizing  the  ground  more  effectually 
than  the  common  toothed  harrow,  but  not  to  the  depth  of  the  disks  or  moving  it  laterally  as 
far. 


104  BULLETIN  No.  104.  [October, 

check.  This  was  due  to  rainy  weather,  which  interrupted  the  plant- 
ing; but  as  sixteen  days  elapsed  between  the  planting  and  the  in- 
spection, there  was  doubtless  ample  opportunity  for  the  transfer  of 
all  living  root-lice  from  the  weeds  to  the  corn, — a  conclusion  to 
which  I  think  no  one  will  take  exception  who  has  been  accustomed  to 
observe  the  corn-field  ant  in  charge  of  the  corn  root-aphis. 

Additional  to  this,  the  difference  in  the  treatment  of  the  plats 
was  the  disking  of  the  experimental  plat  three  times  and  its  harrow- 
ing once,  and  the  differences  between  these  plats  with  respect  to  ants 
and  root-lice  are  to  be  taken  as  due  to  this  additional  and  repeated 
stirring  of  the  soil  of  the  experimental  plat. 

June  10,  two  hundred  and  twenty-five  hills,  distributed  over  five 
different  rows  of  the  experimental  (B)  plat,  were  carefully  exam- 
ined by  Dr.  Folsom  by  digging  up  the  corn  and  counting  the  ants 
and  root-lice  found  upon  the  roots  and  in  the  hills.  The  rows 
chosen  for  these  counts  were  taken  from  various  parts  of  the  field, 
being* respectively  the  first,  seventh,  ninth,  twentieth,  and  thirty- 
second  of  the  entire  plat.  The  last,  it  will  be  noticed,  was  the  row 
next  adjacent  to  the  check  plat.  In  the  latter  plat  (A)  seventy-five 
hills  were  similarly  examined  from  the  first,  second,  and  ninetieth 
rows. 

For  convenience  in  comparison,  the  numbers  given  will  be  those 
for  a  hundred  hills  of  corn  taken  as  a  unit.  It  thus  appears  (see 
Table  I.)  that  twenty-eight  per  cent,  of  the  hills  of  the  check  plat 
(A)  were  infested  with  ants,  and  that  on  the  experimental  plat 
ten  per  cent,  of  the  hills  were  so  infested ;  that  seventeen  per  cent, 
of  the  check  hills  were  infested  by  root-lice,  and  three  per  cent,  of 
the  experimental  hills ;  that  one  hundred  of  the  check  hills  contained 
2263  ants,  and  one  hundred  of  the  experimental  hills,  185  ants;  that 
one  hundred  of  the  check  hills  contained  858  root-lice,  and  one  hun- 
dred of  the  experimental  hills,  79  root-lice.  Or,  more  briefly  stated, 
the  untreated  or  check  part  of  this  field  contained- in  equal  areas, 
about  twelve  times  as  many  ants  and  three  times  as  many  hills  in- 
fested by  them,  and  about  eleven  times  as  many  root-lice  and  six 
times  as  many  hills  infested  by  them,  as  did  the  treated  or  experi- 
mental plat. 


1305.1 


EXPERIMENTS  ON  CORN  INSECTS. 


105 


TABLE  I.     ABSTRACT  OF  COOLJDGE  EXPERIMENT,  1904. 

(Planted  May  13-17  and  May  25;  examined  June  10.) 


Plat  A 

Plat  B 

*Plowed  (1),  harrowed  (2), 
cultivated  (9) 

75  hills  examined 

*Plowed  (1),  disked  three 
times  (3,  4,  5i,  harrowed  (6), 
cultivated  (7),  harrowed  (8) 

225  hills  examined 

Per  cent, 
of 
hills  infested 

Number  of 
insects  per 
hundred  hills 

Per  cent, 
of 
hills  infested 

Number  of 
insects  per 
hundred  hills 

Ants  

28 
17 

2263 
858 

10 
3 

185 
79 

Aphids..  . 

1.  Plowed  May  14  to  16.  2.  Harrowed  May  17.  3.  Disked  May  18.  4.  Disked  May  21. 
5.  Disked  May  25.  6.  Harrowed  May  25.  7.  Cultivated  May  28.  8.  Harrowed  May  30. 
9.  Cultivated  June  9. 

The  Harvel  Experiment.  (Table  II.). — In  the  second  experi- 
ment, made  on  the  farm  of  Mr.  A.  T.  Doerr,  near  Harvel,  in  Chris- 
tian county,  a  field  of  nine  acres  was  divided  into  two  parts,  an 
experimental  plat  of  three  acres  (Plat  B)  and  a  check  plat  (A) 
of  six  acres.  In  this  field  also  the  experimental  plat  consisted  of 
thirty-two  rows  eighty  rods  in  length. 

The  check  plat  (A)  received  no  treatment  until  June  i,  when 
it  was  spaded  and  harrowed.  It  was  planted  June  2  and  harrowed 
June  13,  the  inspection  being  made  the  following  day.  On  the 
experimental  plat  the  stalks  were  harrowed  down,  raked,  and  burned 
May  13,  the  ground  was  plowed  May  23,  harrowed  May  25, 
"spaded"  on  the  26th,  and  harrowed  again  on  the  28th.  At  this 
time  the  field  was  practically  free  from  weeds.  On  the  2Qth  it 
rained  all  day,  the  first  rain  since  the  ground  was  plowed.  This  plat 
was  spaded  and  harrowed  June  I  and  2,  and  planted  on  the  latter 
day.  Rain  followed  on  the  3d  day  of  June,  and  the  weather  was  wet 
until  the  Qth.  The  plat  was  rolled  and  harrowed  on  the  nth  and 
cross-harrowed  on  the  I3th,  the  inspection  following  the  next  day. 
In  this  case  it  will  be  noticed  that  the  whole  field  was  planted  at  the 
same  time. 

The  harrowing  to  break  down  the  stalks  could  scarcely  have  dis- 
turbed the  ground  sufficiently  to  interfere  with  the  operations  of 
the  ants,  and  in  a  comparison  of  the  plats  that  item  may  best  be 
omitted.  The  difference  in  treatment  is  thus  reduced  to  once  plowing, 
once  spading,  harrowing  three  times,  and  rolling  once,  and  to  this 

'Figures  in  parentheses  refer  to  dates  given  at  bottom  of  table. 


106  BULLETIN  No.  104.  [October, 

the  difference  of  the  two  plats  with  reference  to  ants  and  root-lice 
can  fairly  be  attributed. 

For  a  comparison  of  these  plats  seventy-five  hills  of  corn  were 
dug  up  in  the  check  plat  and  one  hundred  in  the  experimental  plat. 
Reducing  the  numbers  given,  for  convenience  of  comparison,  to  a 
unit  of  one  hundred  hills,  it  appears  (Table  II.)  that  sixty-two  per 
cent,  of  the  hills  were  infested  with  ants  on  the  check  plat,  and 
twenty-five  per  cent,  on  the  experimental  plat;  that  forty-four  per 
cent,  of  the  check  hills  were  infested  by  root-lice,  and  eleven  per  cent, 
of  the  experimental  hills ;  that  one  hundred  of  the  check  hills  con- 
tained 1961  ants,  and  one  hundred  of  the  experimental  hills,  630 
ants;  that  one  hundred  of  the  check  hills  contained  1464  root-lice, 
and  one  hundred  of  the  experimental  hills,  198  root-lice.  Or,  more 
briefly  and  generally  stated,  and  comparing  equal  areas  of  the  two 
plats,  we  see  that  the  check  plat  contained  approximately  three 
times  as  many  ants  infesting  two  and  a  half  times  as  many  hills,  and 
seven  times  as  many  root-lice  infesting  four  times  as  many  hills  as 
did  the  experimental  plat. 

The  difference  in  apparent  effect  of  treatment  between  the  Gales- 
burg  field  and  the  Harvel  field  may  have  been  due  to  the  fact  that  the 
Harvel  field  was  much  worse  infested  than  the  other.  Twenty-eight 
per  cent,  of  the  hills  were  infested  with  ants  at  Galesburg  and  sixty- 
two  per  cent,  at  Harvel;  and  seventeen  per  cent,  of  the  hills  were 
infested  with  root-lice  at  Galesburg  and  forty-four  per  cent,  at  Har- 
vel, with  a  difference  of  only  four  days  in  the  dates  of  inspection. 

Where  both  ants  and  root-lice  are  numerous,  the  chances  that 
some  of  the  former  will  find  some  of  the  latter  after  both  have  been 
thoroughly  scattered  through  the  soil,  is  doubtless  greater  than  where 
both  ants  and  root-lice  are  relatively  few.  Of  course,  as  fast  as  root- 
lice  or  their  eggs  are  recovered  by  the  ants,  whether  originally  the 
property  of  the  ants  or  not,  they  will  be  appropriated  and  established 
on  the  plants  in  the  field.  Furthermore,  later  observations  reported 
in  this  paper,  have  made  it  probable  that  ants  actively  convey  their 
charges  from  one  part  to  another  of  the  field  as  conditions  become 
less  favorable  where  they  were  established.  It  is  likely,  consequently, 
that  in  a  crowded  field  the  root-lice  would  be  carried  over  to  plants 
lightly  infested  on  the  experimental  plat,  and  that  the  normal  re- 
sults of  the  treatment  would  be  thus  to  some  extent  masked  or  lost. 

It  is  at  any  rate  made  certain  by  our  later  observations  that  as 
the  food  plant  becomes  crowded,  much  larger  percentages  of  winged 
lice  appear,  and  these,  by  emerging  from  the  ground  and  scattering 
abroad,  tend  to  diminish  the  ratio  of  increase  in  the  over-infested 
field  and  to  increase  it  elsewhere.  Such  a  migration  of  winged  lice 


1905.] 


EXPERIMENTS  ON  CORN  INSECTS. 


107 


would  still  further  diminish  and  mask  the  effect  of  the  treatment. 
In  other  words,  if  an  entire  field  is  treated,  the  benefit  will  be  greater 
than  where  only  an  experimental  plat  is  used,  and  the  results  of 
treatment  here  given  are  less  than  they  should  be  if  they  are  cor- 
rectly to  indicate  the  probable  effect  of  the  procedure  used. 

It  should  be  noticed  further  that  the  treatment  of  the  Coolidge 
and  the  Doerr  fields  was  different  especially  in  the  fact  that  the  lat- 
ter was  harrowed  three  times  while  the  Coolidge  field  was  disked 
three  times.  As  the  harrow  tooth  does  not  penetrate  the  earth  to 
so  great  a  depth  a.c  the  disk,  and  does  not  move  the  dirt  so  far  or 
mix  it  so  well,  much  of  the  difference  in  result  is  probably  attribu- 
table to  this  difference  of  implements. 

TABLE  II.    ABSTRACT  OF  DOERR  EXPERIMENT,  1904. 
(Planted  June  2;  examined  June  J4.) 


Plat  A 

Plat  B. 

*Spaded  (5), 
harrowed  twice  (6,  9) 

75  hills  examined 

*Plowed  (1),  harrowed  (2), 
spaded  (3),  harrowed  (4), 
spaded  (5).  harrowed  («), 
rolled  (7),  harrowed 
twice  (8,  9) 

100  hills  examined 

Per  cent, 
of 
hills  infested 

Number  of 
insects  per 
hundred  hills 

Per  cent, 
of 
hills  infested 

Number  of 
insects  per 
hundred  hills 

Ants   

62 

44 

1961 
1464 

25 
11 

630 
198 

Aphids  

1.  Plowed  May  23.  2.  Harrowed  May  25.  3.  Spaded  (with  spadiner  harrow)  May  26. 
4.  Harrowed  May  28.  5.  Spaded  June  l.  6.  Harrowed  June  2.  7.  Rolled  June  11.  8.  Har- 
rowed June  11.  9.  Harrowed  June  13. 

THE  SEASON  OP  1905.    BRADFORD,  ILLINOIS. 

For  a  further  test  of  agricultural  measures  against  the  corn  root- 
aphis,  I  planned  and  provided  for  a  field  operation  to  begin  as  early 
as  practicable  in  the  spring  of  1905,  in  a  neighborhood  in  Stark 
county  to  which  my  attention  had  been  especially  called  by  the  fol- 
lowing letter  of  March  1 1  from  Messrs.  Deyo  and  Foster,  real  estate 
agents  at  Bradford,  111. 

"The  farmers  here  are  troubled  with  lice  on  the  roots  of  the 
corn.  Even  on  good  ground  we  find  that  the  roots  are  alive  with 
them  and  the  corn  makes  a  very  poor  growth  until  about  harvest- 
time.  If  we  have  rains  it  makes  a  fair  yield,  but  blows  over  very 

*See  note  to  Table  1.,  p.  105. 


108  BULLETIN  No.  104.  [October, 

easily.  Will  you  please  tell  me  what  you  know  in  regard  to  the 
matter,  and  what  has  been  done  on  this  subject." 

Two  assistants  of  the  office,  Mr.  E.  P.  Taylor  and  Mr.  E.  O.  G. 
Kelly,  visited  this  neighborhood  April  6  to  13,  and  after  a  careful 
survey  of  a  large  number  of  farms,  selected  three  for  special  experi- 
ments, belonging  respectively  to  H.  B.  Hinman,  Edward  Finne- 
gan,  and  Frank  Barto.  Special  observations  were  also  made  on  the 
underground  aphids  in  fields  of  corn  and  oats  in  comparison,  on  the 
farm  of  the  F.  H.  Thompson  Estate. 

At  the  time  of  this  first  visit  the  root  aphids  were  all  still  in  the 
egg  stage  in  the  burrows  of  the  small  brown  ant  (Lasius  niger 
alienus).  The  ants  themselves  were  opening  and  extending  their 
burrows,  and  the  aphid  eggs  were  found  in  clusters  in  carefully 
formed  chambers  about  an  inch  under  ground,  in  varying  numbers, 
the  maximum  observed  in  a  single  nest  being  two  hundred  and 
seventy-five.  The  ants  themselves  had  gone  as  deep  as  seven  and  a 
half  inches,  but  no  aphis  eggs  were  found  deeper  than  an  inch.  The 
fields  were  dry,  and  plowing  had  already  begun.  The  soil  was  well 
pulverized,  and  many  ants'  nests  had  been  turned  over  and  covered 
up,  but  were  not  much  broken  up  or  scattered  by  the  plow. 

The  first  aphis  egg  hatched  April  9,  and  several  others  from 
the  same  lot  hatched  the  following  day.  The  young  as  fast  as  they 
left  the  egg  were  placed  by  the  ants  on  the  roots  of  smartweed 
plants.  Many  of  these  weeds  were  from  half  an  inch  to  an  inch 
high,  but  many,  barely  sprouted  and  not  yet  out  of  the  ground,  had 
been  found  by  the  ants,  and  exposed  by  burrowing  along  them.  The 
field  work  at  this  place  was  assigned  to  Mr.  E.  O.  G.  Kelly,  who  de- 
voted his  entire  time  to  it  for  several  weeks. 

The  weather  of  April  and  May  was  so  unusually  wet  as  to  in- 
terfere materially  with  the  intended  treatment  of  the  experimental 
plats.  It  also  prevented  as  frequent  access  to  the  fields  as  was  de- 
sirable for  purposes  of  inspection,  the  exact  comparison  of  check 
and  experimental  plats  being  indeed  delayed  until  May  31,  so  long 
a  time  after  treatment  in  some  cases  as  to  impair  greatly  the  values 
of  these  comparisons.  Illustrations  of  this  point  will  be  given  in 
some  detail  in  the  general  discussion  at  the  conclusion  of  this  paper. 
No  precise  record  was  kept  of  the  rainfall,  but  the  following  memo- 
randa will  be  of  assistance  in  discussing  the  experiments. 

A  light  rain  fell  April  6,  but  from  the  loth  to  the  25th — the 
period  of  plowing — the  weather  was,  on  the  whole,  quite  dry.  April 
27  and  28  heavy  rains  fell,  but  the  fields  were  fairly  dry  again  from 
April  30  to  May  8.  From  the  gth  to  the  I2th  it  rained  hard  and 
frequently,  and  the  soil  was  continuously  wet  to  the  I5th,  when  it 


1905.}  EXPERIMENTS  ON  CORN  INSECTS.  109 

rained  heavily  again,  and  daily  thereafter  to  the  2Oth.  Rains  fell 
again  on  the  2gth  and  3Oth;  and  on  the  4th  of  June. 

The  Hinman  Experiment.  (Table  III.). — On  the  farm  of  Mr. 
Hinman,  four  and  a  half  miles  east  of  Bradford,  was  a  field  of 
seventy  acres  of  corn,  forty  acres  of  which  was  selected  for  a  field 
experiment.  This  had  been  planted  to  corn  each  year  since  1902, 
and  injury  by  the  root-aphis  on  the  higher  parts  of  the  field  had 
been  noticed  in  1904. 

This  forty  was  divided,  for  the  purposes  of  the  experiment,  into 
three  strips.  One  plat  (A)  received  the  usual  preparation  of  the 
land  for  corn.  The  stalks  of  the  old  corn  were  cut,  and  the  ground 
was  plowed  from  April  7  to  28,  harrowed  the  first  time  May  3  and 
4,  pulverized  with  a  disk  harrow  on  May  5,  and  harrowed  again 
May  8.  Plat  C  was  reserved  for  an  experiment  with  minimum 
cultivation.  The  stalks  were  cut,  and  the  ground  was  plowed  April 
7  to  28,  like  the  preceding,  and  harrowed  May  3  and  4  and  again 
May  8.  Plat  B  was  set  aside  for  an  experiment  with  the  effects 
of  maximum  cultivation,  but  repeated  rains  greatly  hindered  the 
farmer's  work,  and  finally,  as  a  consequence,  this  field  was  plowed 
like  the  others  April  7  to  28,  after  the  cutting  of  the  stalks,  was  har- 
rowed May  3  and  4,  disked  May  5  and  again  May  8,  and  har- 
rowed also  on  the  latter  date.  The  preparation  of  these  three  plats 
thus  varied  as  follows : — 

Plat  C  (minimum  cultivation)  differed  from  plat  A,  the  check, 
only  in  the  fact  that  the  ground  was  not  disked.  Plat  B  (maximum), 
on  the  other  hand,  differed  from  the  check  only  in  the  fact  that  it  was 
disked  a  second  time.  B  thus  differed  from  C  by  two  additional 
treatments  with,  the  disk  harrow.  It  will  be  noticed  that  all  the  plats 
were  treated  alike  until  May  5,  when  the  ground  of  two  of  the  plats 
was  first  disked,  and  that  A  and  B  received  identical  treatment  until 
May  8,  when  the  latter  was  disked  a  second  time. 

The  entire  field  was  planted  on  three  different  dates,  the  planted 
rows  running  crosswise  of  the  plats.  The  first  hundred  rows  on  the 
north  end  of  each  plat  were  planted  May  8,  and,  rains  intervening, 
one  hundred  and  sixty-four  rows  next  south  of  these  were  planted 
May  13  and  15.  Rains  again  followed,  so  packing  the  soil  that  the 
remainder  of  the  field — one  hundred  and  eight  rows — was  harrowed 
again  (with  an  Acme  harrow,  sometimes  called  a  pulverizer)  and 
planted  on  the  22d  and  23d  of  May.  This  last-planted  section  thus 
constituted  a  distinct  division  of  the  three  foregoing  plats,  receiving 
one  additional  treatment  with  the  Acme  harrow,  and  being  planted 
two  weeks  later  than  the  first  planting  of  a  hundred  rows  and  about 
a  week  later  than  the  second  planting  of  one  hundred  and  sixty-four 


110  BULLETIN  No.  104.  \_0ctoler, 

rows.  The  extremes  of  treatment  in  this  field,  it  will  be  seen,  were 
between  the  part  of  plat  C  first  planted  and  the  part  of  plat  B 
planted  last,  these  two  plats  differing  in  the  fact  that  the  late- 
planted  part  of  plat  B  was  harrowed  twice  more  (once  with  Acme 
and  once  with  toothed  harrow)  and  disked  once  more  than  the 
early-planted  part  of  C. 

Observations  were  made  in  the  Hinman  field  by  Mr.  Kelly,  at  as 
frequent  intervals  as  the  weather  permitted,  during  the  period  from 
May  2  until  the  planting  was  finished  on  the  23d.  On  May  2,  w7here 
the  ground  had  been  merely  plowed  many  young  root-lice  were  seen 
in  the  field,  which  the  ants  were  placing  on  young  smartweeds.  Five 
ants'  nests,  all  within  a  space  twenty  feet  square,  were  explored  and 
found  to  contain  from  thirty  to  one  hundred  and  thirty-five  ants, 
from  twenty  to  forty  aphis  eggs — green  and  about  to  hatch — and 
from  thirty-five  to  eighty-six  young  root-lice,  all  of  the  first  genera- 
tion from  the  egg.  The  harrowing  of  the  whole  field  May  3  and 
4  stirred  the  weeds  about  and  disturbed  the  ants  and  aphids,  but 
seemed  to  kill  neither  insects  nor  weeds.  The  disk  harrow  or  pul- 
verizer loosened  the  soil  to  the  full  depth  of  the  plowing,  and  scat- 
tered the  ants  and  aphids  greatly.  On  the  6th  of  May  ants  were 
everywhere  on  and  through  the  soil,  and  an  occasional  aphis  was 
seen  on  roots  of  grass  or  smartweed,  seldom,  however,  with  any  ants 
in  company.  May  13,  the  ants  were  generally  reestablished  in  the 
plowed  part  of  the  field,  and  many  root-lice  were  collected  from  their 
burrows  feeding  on  foxtail-grass  and  on  an  occasional  volunteer 
plant  of  corn.  Thirty-two  ants'  nests  were  dug  out  on  this  date, 
each  containing  from  six  to  one  hundred  ants.  In  seventeen  nests 
there  were  no  root-lice,  and  in  the  remaining  fifteen  these  varied  in 
number  from  two  to  sixty-five.  There  were,  on  an  average,  twenty 
aphids  to  each  nest  containing  them,  all  wingless,  but  many  already 
full  grown,  and  all  apparently  of  the  first  generation  from  the  egg. 
May  1 8,  the  corn  planted  May  8  was  beginning  to  come  up,  and 
twenty-five  hills  were  dug  out.  Ants  were  found  in  two ;  root-lice 
in  none. 

May  31,  a  test  examination  of  this  field  was  made  by  digging  up 
in  the  earliest-planted  portions  of  plats  A,  B/  and  C,  fifty  hills 
from  each,  and  in  the  later-planted  portions  fvventy-five  hills  from 
each  plat.  Although  the  number  of  hills  dug  up  wat-  perhaps  too 
small  to  give  satisfactory  averages  applicable  to  the  entire  field, 
Mr.  Kelly  tells  me  that  the  several  lots  were  not  taken  entirely  at 
random,  but  that  each  was  carefully  chosen  with  the  idea  of  making 
it  a  fair  and  sufficient  sample  of  its  plat.  In  digging  up  the  plants 
the  whole  root  system  was  exposed,  and  all  the  ants  and  all  the  root- 


1905.} 


EXPERIMENTS  ON  CORN  INSECTS. 


Ill 


lice  were  collected  and  counted  for  each  hill.  For  convenience  in 
comparison  the  data  will  be  given  in  each  instance  for  a  hundred 
hills  of  corn  taken  as  a  unit.  Those  for  the  early  and  late  plantings 
will  be  given  separately — first  those  for  the  parts  of  the  field  which 
received  the  least  treatment,  and  then,  by  successive  steps,  for  those 
which  were  treated  most.  (See  Table  III.) 

TABLE  I  [I.     ABSTRACT  OF  HINMAN  EXPERIMENT,  1905. 
(Planted  May  8,  and  May  13  to  15;  examined  May  31.) 


Plat  A.  i 

Plat  B,  1 

Plat  C,  1 

*Plowed  (!).  harrowed 
(2),  disked  (3),  har- 
rowed (4) 

50  hills  examined 

Plowed  (1).    harrowed 
(2),  disked  twice 
(3,  5),  harrowed  (4) 

50  hills  examined 

Plowed  (1),  harrowed 
twice  (2,  4) 

50  hills  examined 

Percent, 
of 
hills 
infested 

Number 
of  insects 
per  hun- 
dred hills 

Per  cent, 
of 
hills 
infested 

Number 
of  insects 
per  hun- 
dred hills 

Percent. 
of 

hllis 
infested 

Number 
of  insects 
per  hun- 
dred hills 

Ants  

54 
40 

2012 
838 

26 
12 

744 
158 

64 

48 

2096 
974 

Aphids  

A,  2.    Pulverized  (8) 
25  hills  examined 

B,  2.    Pulverized  (6) 
25  hills  examined 

C,  2.    Pulverized   (6) 
25  hills  examined 

Ants.  .      ..... 
Aphids  

24 
12 

260 
62 

12 

0 

66 
0 

24 

20 

194 

146 

1.  Plowed  April  7  to  28.  2.  Harrowed  May  3  and  4.  3.  Disked  May  5.  4.  Harrowed 
May  8.  5.  Disked  May  8.  6.  Pulverized  (Acme  harrow)  May  22  and  23. 

In  plat  C,  with  minimum  treatment,  sixty-four  per  cent,  of 
the  hills  were  infested  with  ants ;  in  plat  A,  with  medium  treatment, 
fifty-four  per  cent,  were  so  infested;  and  in  plat  B,  with  maxi- 
mum treatment,  the  percentage  of  infestation  by  ants  was  twenty- 
six.  Forty-eight  per  cent,  of  the  hills  of  plat  C  were  infested  by 
root-lice ;  forty  per  cent,  in  plat  A ;  and  twelve  per  cent,  in  plat  B. 
One  hundred  hills  in  plat  C  contained  2096  ants;  in  A,  2012;  and 
in  B,  744.  One  hundred  hills  in  C  contained  974  root-lice;  in 
A,  838;  and  in  B,  158.  In  other  words,  taking  the  infestation  of 
plat  C  as  a  basis  of  comparison,  we  find  that  the  single  additional 
disking  of  plat  A  reduced  the  number  of  hills  infested  by  ants  to 
eighty-four  per  cent.,  and  those  infested  by  root-lice  to  eighty-three 

*See  note  to  Table  I.,  p.  105. 


112  BULLETIN  No.  104.  [October, 

per  cent.,  the  number  of  ants  per  hundred  hills  to  ninety-five  per 
cent.,  and  the  number  of  rootrlice  per  hundred  hills  to  eighty-six  per 
cent.  Comparing  similarly  plat  B  with  plat  C,  we  find  that  the  ef- 
fect of  disking  twice  was  to  reduce  the  number  of  hills  of  corn  in- 
fested by  ants  to  forty-one  per  cent.,  and  the  number  infested  by 
root-lice  to  twenty-five  per  cent.,  and  also  to  reduce  the  number  of 
ants  per  hundred  hills  of  corn  to  thirty-five  per  cent.,  and  the  number 
of  root-lice  per  hundred  hills  to  sixteen  per  cent.  Still  more  briefly 
stated,  the  root-louse  infestation  was  reduced  approximately  fifteen 
per  cent,  by  disking  once ;  and  seventy-five  per  cent,  as  to  the  num- 
ber of  hills  infested,  or  eighty-four  per  cent,  as  to  the  number  of 
root-lice  in  the  field,  by  disking  twice  (see  experiment  5,  Table  V.). 

A  comparison  of  the  early-planted  part  of  section  C,  in  which 
fifty  hills  were  examined,  with  the  late-planted  part  of  section  Br 
in  which  twenty-five  hills  were  examined,  gives  a  surprising  contrast. 
It  will  be  remembered  that  all  the  latest-planted  sections  received 
an  additional  pulverizing  just  before  planting, — necessitated,  in 
the  owner's  judgment,  by  the  packing  effect  of  a  heavy  rain  while 
the  planting  of  the  field  was  in  progress.  If  this  circumstance  be 
taken  into  account,  then  it  may  be  said  that  a  comparison  of  these 
two  areas  indicates  that  three  times  disking — the  last  time  soon  after 
a  heavy  packing  rain — may  reduce  the  number  of  hills  infested  by 
ants  to  nineteen  per  cent.,  and  the  number  of  ants  themselves  to  three 
per  cent.,  and  may  obliterate  the  root-lice  entirely,  since  none  were 
found  in  the  twenty-five  hills  searched  in  the  late-planted  part  of 
section  B. 

The  effect  of  a  single  disking,  following  closely  upon  a  beating 
rain,  as  shown  by  counts  made  in  each  of  the  three  sections  before 
and  after  these  events  and  by  averaging  the  percentages  for  the 
three  plats,  is  as  follows :  The  hills  infested  by  ants  were  reduced 
to  forty-three  per  cent,  and  the  ants  themselves  to  ten  per  cent,  of 
the  number  to  be  found  in  those  parts  of  the  field  which  had  not 
been  disked  after  the  rain,  while  the  root-lice  were  reduced  by  the 
same  treatment,  to  thirty-six  per  cent,  in  the  number  of  hills  infested 
and  to  eleven  per  cent,  in  the  number  of  insects  in  the  field. 

A  further  instructive  conclusion  may  be  deriv.ed  from  the  obser- 
vations of  May  31  by  comparing  the  product  of  fifty  badly  infested 
hills  with  the  remaining  225  dug  up  on  that  day.  The  total  number 
of  root-lice  found  in  the  fifty  hills  was  5254,  averaging  over  105  per 
hill,  while  the  total  in  the  225  hills  was  1068,  or  an  average  of  five 
per  hill.  If  these  two  collections  of  root-lice  be  compared  with 
reference  to  the  percentage  of  the  adults  which  have  developed 
wings,  added  to  the  pupae,  which  would  acquire  them  at  the  next 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  113 

molt,  we  find  that  this  ratio  of  winged  forms  is  much  greater  in  the 
badly  infested  hills;  that  the  ratio  of  winged  specimens  increases, 
in  other  words,  with  the  crowding  of  the  insects  and  the  conse- 
quent pressure  on  their  food  supply.  In  the  225  slightly  infested 
hills  were  225  wingless  adults  and  54  winged  adults  and  pupae,  a 
ratio  of  21  per  cent. ;  while  in  the  fifty  badly  infested  hills  were  227 
wingless  adults  and  349  winged  adults  and  pupae,  a  ratio  of  64  per 
cent,  of  the  winged  form.  That  is,  the  winged  insects  were  three 
times  as  numerous  in  the  crowded  colonies  as  they  were  in  the 
smaller  ones.  It  is  quite  probable  that  experiment  will  show  that 
this  increase  of  the  ratio  of  winged  to  wingless  specimens  might  be 
brought  about  experimentally  by  various  means  which  have  the  effect 
to  diminish  the  average  food  supply.  It  is  to  be  expected,  conse- 
quently, that  mere  drouth,  if  it  goes  to  the  extreme  of  injuring  the 
plant  infested,  may  have  the  effect  to  break  the  force  of  the  root- 
louse  attack  by  stimulating  the  development  of  winged  specimens, 
which,  leaving  the  earth  and  flying  abroad,  would  give  the  infested 
plant  a  chance  to  rally  against  injury. 

The  Finnegan  Experiment.  ( Table  IV.). — On  the  farm  of  Ed- 
ward Finnegan,  one  and  a  half  miles  northeast  of  Bradford,  a  field 
of  eighteen  acres  was  selected  for  experiment.  This  field  had  been 
planted  to  corn  in  1904,  to  oats  in  1903,  and  to  corn  for  the  three 
preceding  years.  A  considerable  injury,  apparently  due  to  the  corn 
root-aphis,  had  been  noticed  in  it  in  1904.  Two  parts  of  this  field, 
which  may  be  called  plats  A  and  B,  were  treated  as  follows : — 

Both  were  plowed  April  18  to  21,  disked  May  22,  harrowed 
May  23  and  24,  and  planted  May  24.  B  differed  from  A  only 
in  the  fact  that  it  was  twice  disked  in  succession  May  22,  instead  of 
once  only  on  that  date.  Plat  B  was  a  strip  running  lengthwise 
of  the  field  from  north  to  south,  and  twenty-two  rows  wide,  begin- 
ning on  the  west  side;  and  plat  A  comprised  the  greater  part  of 
the  field,  extending  eighty-eight  rows  inward  from  the  eastern 
border.  Smartweed  and  grass  grew  two  or  three  inches  high  by 
May  22,  heavy  rains  having  by  this  time  packed  the  soil  very  closely. 
The  corn  was  put  in  about  three  inches  deep,  and  began  to  show 
above  the  surface  by  May  30,  on  which  date  the  first  root-aphis  was 
found  in  a  hill  of  corn  infested  by  Lasius  alienus.  These  fields  were 
examined  June  9  for  a  test  of  the  results  of  the  single  additional 
treatment  with  the  disk  harrow  in  which  alone  the  two  plats  differed 
(see  Table  IV.).  Fifty  hills  were  examined  from  each  plat,  with 
the  general  result  that  in  the  check  plat,  A,  seventy-five  per  cent, 
of  them  were  infested  by  ants,  and  that  in  the  experimntal  plat, 
B,  fifty  per  cent,  of  them  were  so  infested.  In  the  check  plat,  A, 


114 


BULLETIN  No.  104. 


f  October , 


seventy-four  per  cent,  of  the  hills  were  infested  by  root-lice,  and 
forty-four  per  cent,  in  the  experimental  plat.  The  former  con- 
tained 3034  ants  per  hundred  hills,  and  the  latter  1746 — fifty-seven 
per  cent,  of  the  first  number.  The  latter,  or  check  plat,  also  con- ' 
tained  2392  root-lice  per  hundred  hills,  and  the  former,  or  experi- 
mental plat,  1362  root-lice  per  hundred  hills — sixty  per  cent,  of  the 
number  in  the  first. 

More  briefly  stated,  the  single  treatment  with  the  disk  harrow 
May  22,  following  immediately  upon  an  earlier  treatment  the  same 
day  (see  Experiment  4,  Table  V.),  had  reduced  the  infestation  by 
ants  by  forty-two  per  cent,  in  number  of  insects  and  by  thirty-three 
per  cent,  in  number  of  hills  infested ;  and  had  reduced  the  infesta- 
tion by  root-lice  by  forty-three  per  cent,  in  number  of  insects  and 
by  forty-one  per  cent,  in  number  of  hills  infested,  the  result  being 
tested  by  a  critical  examination  made  sixteen  days  after  the  field 
was  planted.  In  short,  a  single  disking  of  the  soil  had  diminished 
the  infestation  by  ants  and  root-lice  generally  by  something  over  one 
third. 

TABLE  IV.    ABSTRACT  OF  FINNEGAN  EXPERIMENT,  1905. 

(Planted  May  24;  examined  June  9.) 


Plat  A 

Plat  B 

*Plowed  (1),  disked  (2), 
harrowed  (4) 

Plowed  (1),  disked  twice  (2,  3). 
harrowed  (4) 

50  hills  examined 

50  hills  examined 

Per  cent, 
of 
hills  infested 

Number  of 
insects  per 
hundred  hills 

Per  cent, 
of 
hills  infested 

Number  of 
insects  per 
hundred  bills 

Ants  

75 
74 

3034 
2392 

50 
44 

1746 
1362 

Aphids  

1.  Plowed  April  18  to  21.     2.  Disked  first   time   May  22.      3.  Disked   second   time   May  22. 
4.  Harrowed  Maj  23  and  24. 

Observations  on  the  Barto  Farm. — A  field  of  seventy  acres, 
forty-five  in  oats  and  the  remainder  in  corn,  on  the  farm  of  Mr. 
Frank  Barto,  near  Bradford,  111.,  was  selected  for  observation  be- 
cause of  the  extraordinary  abundance  of  ants'  nests  containing  aphis 
eggs  to  be  found  in  various  parts  of  it,  and  because  of  the  history  of 
the  oats  fields  with  reference  to  corn  preceding,  and  of  one  of  the 
corn  fields  with  reference  to  oats.  It  was  the  principal  object  of  the 
observations  here  made,  to  ascertain  the  effect  on  the  corn  root-aphis 
of  a  change  of  crop  from  corn  to  oats. 

*See  note  to  Table  I.,  p.  105. 


1905.']  EXPERIMENTS  ON  CORN  INSECTS.  115 

For  the  purposes  of  this  discussion  the  field  may  be  divided  into 
two  parts :  one  of  twenty  acres  of  corn  which  had  been  in  that  crop 
continuously  for  at  least  three  years  preceding — five  acres  indeed 
having  been  in  corn  since  1899;  and  the  other  of  forty-five  acres 
of  oats,  thirty-five  acres  of  which  had  been  in  corn  for  three  years 
preceding,  and  ten  acres  continuously  in  that  crop  since  1899  unt^ 
sowed  to  oats  the  present  spring. 

April  27  several  nests  of  Lasius  alienus  were  explored,  each 
containing  numerous  root-louse  eggs  and  some  root-lice.  Above 
and  immediately  about  the  ants'  nests  the  smartweed  was  withering 
and  the  roots  were  drained  of  sap,  and  in  many  cases  blackened  and 
decayed.  The  tunnels  of  the  ants  extended  sometimes  as  far  as  a 
foot  and  a  half  from  the  main  entrance,  and  ranged  irregularly  from 
a  depth  of  an  inch  to  about  six  inches.  The  root-lice  were  mainly 
on  smartweed  (Polygonum)  roots,  from  sixteen  to  twenty  on  a 
single  plant.  In  that  part  of  the  field  which  had  been  six  years  in 
corn  and  was  to  be  planted  to  the  same  crop  again  this  year,  eighteen 
nests  were  found  within  a  distance  of  two  hundred  hills;  and  in 
that  part  which  had  been  in  corn  for  the  three  preceding  years,  thirty 
nests  were  found  between  two  rows  three  hundred  and  fifty  hills 
in  length.  Twelve  of  the  nests  were  explored  in  these  parts  of  the 
field,  five  in  the  first  mentioned  and  seven  in  the  second.  The  ants 
in  these  colonies  ranged  in  number  from  eighteen  to  one  hundred 
and  twenty-six,  averaging  fifty-seven  each.  Four  of  them  contained 
from  one  hundred  to  three  hundred  larvae  and  eggs  of  ants.  All 
were  plentifully  stocked  with  the  eggs  and  young  of  root-lice> 
whether  in  all  cases,  or  even  in  the  majority,  those  of  Aphis  maidi- 
radicis  (the  corn  root-aphis)  it  was  impossible  to  say  with  cer- 
tainty at  that  early  date.  Root-louse  eggs  varied  in  number  from 
seventy-five  to  two  hundred  and  seventy-five  per  nest,  averaging 
one  hundred  and  sixty-one,  and  young  root-lice  were  found  in  num- 
bers varying  from  two  to  seventy-eight,  with  an  average  of  thirty- 
five,  a  total  average  of  one  hundred  and  ninety-six  root-louse  eggs 
and  young  to  each  ant's  nest. 

May  i,  root-lice  nearly  full  grown,  together  with  many  young, 
were  taken  from  roots  of  smartweed  and  ragweed  (Ambrosia)  in 
that  part  of  the  field  sown  to  oats  this  spring  but  in  corn  for  three 
year  preceding.  Two  hundred  oats  plants  were  examined  on  and 
near  the  nests  of  ants  containing  root-lice,  but  not  a  louse  was  found 
upon  them.  Here  again  smartweeds  near  the  nests  of  ants  were 
withered  and  the  roots  were  dead  or  actually  gone.  Cavities  and 
gangways  had  been  made  by  the  ants  beside  the  roots  of  these  weeds. 
The  first  root-louse  of  the  second  generation  was  seen  in  the  field 


116  BULLETIN  No.  104.  [October, 

May  3,  although  the  eggs  of  the  preceding  year  were  not  yet  all 
hatched. 

At  this  time  an  interesting  and  important  comparison  was  made 
between  the  contents  of  ants'  nests  in  fields  of  corn  last  year  and 
those  on  which  a  single  crop  of  oats  had  been  raised.  Every  nest 
of  the  former  contained  numerous  root-lice  or  their  eggs,  while  thir- 
teen nests  of  Lasius  alienus  found  in  the  oats  field  in  corn  for  the 
three  preceding  years  were  carefully  explored,  but  not  an  aphis 
could  be  found  in  the  possession  of  the  ants.  Later,  a  single  colony 
of  thirty-six  ants  was  found  with  no  eggs  but  with  seventy-eight 
root-lice  in  their  possession.  These  had  very  likely  been  carried  in 
from  an  adjacent  part  of  the  field.  In  the  absence  of  root-lice  the 
ants  seemed  to  be  maintaining  themselves,  in  part  at  least,  by  cap- 
turing beetles  and  insect  larvae,  the  remains  of  which  were  found  in 
their  nests. 

On  the  other  hand,  in  the  oats  fields  which  had  been  in  corn  for 
some  years  before,  ants  were  now  less  abundant  than  in  the  adjacent 
corn,  and  the  eggs  and  young  of  root-lice  were  common  in  their 
nests.  In  fourteen  nests  explored  May  3,  eight  hundred  and  eighty- 
six  ants  were  found,  an  average  of  sixty-three  per  nest,  together 
with  five  hundred  and  sixty-five  eggs  and  eight  hundred  and  eight- 
;en  young  of  root-lice.  This  was  an  average  of  ninety-eight  to 
each  nest,  and  is  to  be  compared  with  the  average  of  one  hundred 
and  ninety-six  root-lice  and  root-louse  eggs  per  nest  in  the  adjacent 
fields  of  corn. 

By  May  8  the  second  generation  of  the  root-lice  was  abundant 
in  the  oats  fields,  but  none  of  them  had  as  yet  acquired  wings.  Heavy 
rains  fell  on  the  loth  and  nth  of  May  and  at  occasional  intervals 
thereafter,  and  the  muddy  fields  were  not  revisited  until  May  18. 
Then  many  ants  were  crawling  about  and  making  new  burrows 
in  the  ground  (each  of  which  contained  from  two  to  ten  ants, 
and  no  root-lice.  Specimens  of  the  latter,  dropped  near  these 
new-made  burrows,  were  promptly  pounced  upon  by  ants  and 
carried  under  ground.  The  root-lice  seemed  to  be  less  numerous 
than  before,  as  if  affected  by  the  rains.  On  the  22d  of  May  the 
fields  continuously  in  corn  were  visited  again,  and  fourteen  nests 
of  ants  were  dug  out  and  the  contents  caught  and  counted.  Five 
hundred  and  seventy-one  ants  were  found  in  these  nests,  an  aver- 
age of  forty-one  each,  and  six  hundred  and  fifty-five  ant  larvae 
in  eight  of  them.  The  aphis  contents,  on  the  other  hand,  had 
dwindled  greatly,  consisting  of  forty-six  wingless  adults,  thirty- 
three  pupae,  and  one  hundred  and  seventy-three  young,  a  total  aver- 
age of  thirty-seven  to  each  ant's  nest. 


1905.}  EXPERIMENTS  ON  CORN  INSECTS.  117 

May  30  the  oats  fields  were  revisited  by  Mr.  Kelly,  in  company 
with  Mr.  C.  A.  Hart,  whom  I  had  sent  out  from  the  office  to  inspect 
the  situation,  and  to  the  astonishment  of  both  not  an  ant  nor  an 
aphis  could  be  found  in  the  whole  forty-five  acres  of  this  crop.  As 
recent  rains  had  fallen,  it  was  at  first  surmised  that  the  ants'  bur- 
rows had  merely  been  obliterated,  but  protracted  search  on  the  two 
following  days,  which  were  warm  and  bright,  gave  the  same  nega- 
tive result.  The  smartweeds  were  now  virtually  all  dead,  and  the 
oats  were  tall  enough  to  shade  the  ground.  The  entire  ant  and  aphid 
population  of  these  fields  had  evidently  abandoned  them,  and  could 
not  be  traced. 

June  22  another  visit  was  made  to  this  field,  and  prolonged 
search  again  failed  to  discover  a  single  insect  of  either  kind,  al- 
though in  the  adjoining  corn  both  ants  and  aphids  were  numerous, 
and  in  one  of  the  fields,  where  nearly  every  hill  was  infested,  con- 
siderable injury  was  being  done.  The  field  of  corn  which  had  been 
in  oats  the  preceding  year,  and  in  which  on  previous  visits  ants  were 
found  but  not  a  root-louse,  was  now  badly  infested,  and  this  fact 
offered  the  only  possible  hint  of  the  whereabouts  of  the  insects  which 
had  left  the  oats  the  preceding  month. 

Observations  in  the  Thompson  Field. — For  further  evidence 
concerning  the  effects  of  a  change  from  corn  to  oats,  observations 
were  made  by  Mr.  Kelly  on  two  adjacent  fields  of  forty  acres  each, 
one  in  corn  this  spring  and  the  other  in  oats,  both  fields  having  been 
in  corn  continuously  for  the  three  years  preceding,  and  both  being 
heavily  infested  by  Aphis  maidiradicis  May  8,  when  first  selected 
for  this  comparison. 

May  19,  the  ground  being  very  wet  after  a  recent  rain,  eight  ant 
hills  were  examined  in  the  oats  field  and  their  contents  collected. 
Three  hundred  and  thirty-four  ants  were  obtained,  an  average  of 
forty-two  to  each  colony,  and  one  hundred  and  sixty-seven  aphids, 
an  average  of  twenty-one  to  each  ant's  nest.  Fifty  of  these  aphids 
were  wingless  adults  and  eight  were  pupae,  the  remainder,  of  course, 
being  young  in  various  stages.  These  were  contained  in  seven  of 
the  nests,  one  nest  being  without  root-lice.  The  number  varied  from 
two  to  forty-six  to  a  nest. 

The  other  field  had  been  plowed  for  corn  April  28  to  May  5, 
and  harrowed  twice.  Hard  rains  following,  it  was  disked  twice 
May  19  and  20,  and  harrowed  again  just  as  it  was  planted.  Both 
ants  and  root-lice  were  found  in  this  corn  May  20,  but  no  record  was 
made  of  their  number  or  distribution  until  June  2,  at  which  time  a 
final  visit  was  made  for  a  comparison  of  the  two  fields. 

In  the  oats  not  an  ant  nor  an  aphid  could  now  be  found ;  even 
the  borders  of  the  field  nearest  the  corn  had  been  completely  aban- 


118  BULLETIN  No.  104.  [October, 

doned  by  both.  In  the  corn,  from  a  hundred  hills  chosen  as  fairly 
representative  of  the  whole  field  2156  ants  were  taken,  an  average 
of  twenty-two  to  the  hill,  fifty-two  of  the  hundred  hills  being  in- 
fested by  them.  In  the  same  hills  1507  root-lice  were  found,  an 
average  of  fifteen  to  the  hill,  forty-three  of  the  hills  being  infested. 
Each  ant's  nest  contained  on  an  average  forty-one  ants  and  thirty- 
five  root-lice, — less  than  one  root-louse  to  each  ant.  The  winged  lice 
in  these  hundred  hills  averaged  in  number  twenty-seven  per  cent, 
of  all  the  adults.  Collections  made  on  higher  and  drier  parts  of  the 
field  were  compared  with  those  from  lower  and  wetter  portions,  but 
gave  no  marked  difference  in  respect  either  to  the  ants  or  aphids,  or 
to  the  ratios  of  winged  to  wingless  adults. 

Observations  made  in  this  field  correspond  precisely,  it  will' be 
seen,  to  those  reported  from  the  Barto  fields  with  reference  to  the 
total  disappearance,  late  in  May,  of  ants  and  aphids  from  oats  grown 
on  old  corn  ground. 

ADDITIONAL  MISCELLANEOUS  OBSERVATIONS. 

April  n,  at  Bradford,  an  ant's  nest  was  explored,  the  burrows 
of  which  extended  throughout  an  area  approximately  three  by  four 
feet,  and  to  depths  varying  from  one  to  four  inches.  Ants  were  dis- 
tributed everywhere  through  the  soil  within  these  dimensions,  but 
all  the  aphis  eggs  seen  were  collected  at  one  place. 

April  12,  a  nest  of  Lasius  alienus,  around  which  a  few  young 
smartweeds  (Polygonum  persicaria)  about  one  inch  high  were  scat- 
tered, was  watched  by  Mr.  Kelly  for  two  hours  and  a  half.  An  ant 
coming  up  with  a  young  root-louse  in  its  mandibles  carried  this 
about  two  feet  and  placed  it  on  a  smartweed  very  near  the  ground, 
and  the  root-louse,  after  crawling  about  half  an  inch,  thrust  its  beak 
into  the  plant.  Six  more  ants  transferred  a  single  root-louse  each 
to  smartweeds  above  ground  within  the  next  twenty  minutes.  In 
about  an  hour  and  a  half  one  of  the  ants  returned  its  root-louse  to 
the  nest,  and  thirty-five  minutes  later  all  had  been  carried  back.  One 
of  these  ants,  which  was  so  marked  that  it  could  be  recognized  on 
its  return,  recovered  and  carried  to  the  nest  the  same  root-louse 
which  it  had  previously  brought  out. 

Another  nest  of  the  ants  was  carefully  explored  on  the  I3th. 
The  burrows  were  found  to  vary  in  diameter  from  one  sixteenth  to 
three  eighths  of  an  inch,  and  to  range  from  one  to  six  inches  below 
the  surface.  In  a  cell  a  quarter  of  an  inch  in  diameter  were  many 
eggs  and  a  few  young  of  the  corn  root-aphis.  When  these  were  dis- 
turbed the  ants  seized  them  and  retreated  to  more  distant  parts  of 


1905.1  EXPERIMENTS  ON  CORN  INSECTS.  119 

their  habitation.  About  two  inches  from  this  collection  of  eggs  a 
smartweed  root  had  been  exposed  by  the  ants  under  ground,  and  on 
this  about  fifteen  of  the  root-lice  were  feeding. 

In  another  nest  explored  on  the  same  day  the  burrows  were 
from  one  tenth  to  one  eighth  of  an  inch  in  diameter.  Under  a  space 
of  two  square  feet  four  clusters  of  root-louse  eggs  and  some  recently 
hatched  aphids  were  found.  Six  young  aphids  on  the  roots  of  a 
smartweed  in  one  of  these  burrows  were  promptly  seized  by  the  ants 
and  carried  farther  into  their  retreat.  At  four  o'clock  p.  m.  most  of 
the  ants  had  retired  for  the  day,  but  two  brought  out  an  aphis  each, 
taking  it  back,  however,  in  less  than  two  minutes.  Twenty-two 
ants  were  found  in  this  nest,  together  with  a  bunch  of  aphis  eggs 
about  as  large  as  a  pea.  Two  inches  from  this  mass  of  eggs  was  a 
sprouting  smartweed  that  had  not  yet  broken  ground,  and  on  it  were 
a  number  of  young  root-lice.  When  exposed  by  digging,  the  ants 
immediately  seized  them  and  carried  them  away.  Roots  of  smart- 
weed,  grasses,  and  ragweed  exposed  in  burrows,  sometimes  had  no 
root-lice  on  them,  although  in  one  case  a  root-louse  was  found  on  a 
ragweed  root. 

May  5  ten  nearly  grown  aphids  were  taken  from  a  smartweed 
root  and  placed  on  the  bare  ground.  They  crawled  actively  about 
and  two  of  them  entered  a  crack  in  the  earth  as  if  to  escape  the  light. 
One  of  these  was  found  by  an  ant  which  carried  it  away.  Two  small 
ones  crawled  about  four  feet  and  stopped  as  if  exhausted,  but  two 
larger  aphids  traveled  more  than  ten  feet  in  an  hour  and  twenty  min- 
utes. All  these  aphids  were  seemingly  averse  to  the  light,  and 
crawled  away  from  the  sun. 

May  8  several  young  of  the  second  brood  were  found.  Three 
full-grown  stem-mothers  were  unearthed,  near  one  of  which  were 
four  young,  and  near  another,  two.  The  third  was  in  the  act  of 
giving  birth  to  an  aphis,  of  which  an  ant  took  possession  as  soon  as 
it  was  born  and  carried  it  to  a  new  plant.  Presently  all  the  other 
young  were  carried  away  by  ants  and  placed  on  plant  roots.  A 
second  aphis  was  born  from  the  same  mother  within  forty  minutes 
after  the  first.  This  also  was  soon  carried  away  and  placed  on  a 
fresh  plant. 

On  the  Qth,  which  .was  cool  and  damp,  a  heavy  rain  having  fallen 
during  the  morning,  the  ants  were  seen  taking  the  root-lice  from  the 
old  smartweed  roots — which  were  now  dead  and  dry  or  even  de- 
cayed— and  placing  them  on  the  roots  of  younger  plants. 

On  May  12  Mr.  Kelly  took  a  corn  root-aphis  from  a  plant  and 
placed  it  on  the  ground.  A  root-louse  ant  (Lasius  alienus}  found  it 
presently,  carried  it  away  to  a  distance  of  four  feet,  placed  it  on  the 


120  BULLETIN  No.  104.  [October, 

ground,  made  a  burrow  to  the  root  of  a  plant  of  foxtail-grass  (5V- 
taria)  and  put  the  root-louse  on  the  plant,  where  it  was  afterwards 
found  by  digging.  Presently  she  took  the  root-louse  away  again  to 
.a  new  place,  and  finding  a  root  of  foxtail  exposed  in  a  crack  of  the 
earth  she  placed  the  aphis  on  it,  and  there  the  insect  remained  until 
the  observation  closed. 

April  23  a  Harpalus  caliginosus  was  found  in  an  ant's  (Lasius 
alienus}  nest,  where  it  was  surrounded  by  several  fragments  of  ants 
which  it  had  evidently  been  eating.  April  26  another  harpalid  was 
captured  under  a  board,  where  it  was  eating  ants  and  was  sur- 
rounded by  fragments  of  those  already  devoured. 

April  29  the  remains  of  four  seed-corn  beetles  (Agonoderus  pal- 
lipes)  were  seen  in  an  ant's  nest  which  contained  about  two  hundred 
ants,  but  no  root-lice.  May  1.5  a  Lasius  alienus  was  found  feeding 
on  an  earthworm. 

Systematic  breeding-cage  experiments,  made  in  my  insectary  at 
Urbana  with  eggs  and  aphids  sent  in  by  Mr.  Kelly,  gave  results  sub- 
stantially consistent  with  those  previously  published*  as  to  periods 
and  succession  of  generations,  but  yielded  a  much  larger  number 
of  young  for  each  mother  aphis  than  I  have  previously  reared.  The 
largest  number  hitherto  reported  was  fifteen  young,  and  the  average 
reared  was  much  less  than  that.  This  year,  however,  thirty-six 
adults  bred  between  July  i  and  September  14  produced  from  twenty 
to  eighty-four  young  each,  with  an  average  of  forty-one  to  each  par- 
ent, and  this  may  probably  be  accepted  as  the  known  rate  of  multipli- 
cation under  favorable  conditions.  The  period  of  development  from 
birth  to  reproductive  maturity,  as  shown  by  the  birth  of  the  first 
young,  varied  from  seven  to  ten  days  for  twenty-three  specimens,  the 
average  being  8.4  days.  The  time  from  the  appearance  of  the  first 
young  of  any  parent  to  the  birth  of  the  last  young  of  the  same 
parent  varied,  in  thirty-six  cases,  from  6  to  20  days,  with  an  average 
of  10  days,  and  this  may  be  taken  as  the  ordinary  length  of  the 
reproductive  period  in  midsummer  under  insectary  conditions. 

GENERAL  DISCUSSION  OF  THE  RESULTS  (TABLE  V.). 

The  most  pronounced  effect  of  an  early  treatment  of  the  soil  for 
the  control  of  the  corn  root-aphis  was  produced  on  the  Coolidge 
farm  in  1904,  where  disking  three  times  and  harrowing  once  re- 
duced the  number  of  hills  infested  by  ants  by  sixty-four  per  cent., 
and  those  infested  with  aphids  by  eighty-two  per  cent.,  and  the  num- 
ber of  insects,  both  ants  and  aphids,  by  ninety-two  per  cent.  each. 


*Eighteentb  Rep.  State  Ent.  111.,  pp.  63-64. 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  121 

In  this  case  the  field  was  disked  on  the  i8th,  2ist,  and  25th  of  May, 
harrowed  on  the  latter  date,  and  examined  June  9,  fifteen  days  after 
the  last  treatment. 

More  remarkable,  on  the  whole,  was  the  effect  of  once  harrowing 
with  an  Acme  harrow  May  22  and  23,  after  numerous  heavy  rains 
from  the  I5th  to  the  2Oth  of  May,  1905.  Here  a  single  treatment 
(Experiment  3,  Table  V.)  with  the  disk  harrow,  used  as  soon  as 
the  ground  was  dry  enough  to  work  properly,  reduced  the  number 
of  hills  infested  by  ants  and  aphids  by  fifty-eight  per  cent,  and  sixty- 
four  per  cent,  respectively,  and  the  number  of  insects  in  the  field  by 
ninety  per  cent,  for  the  ants  and  eighty-nine  per  cent,  for  the  aphids. 

The  least  effective  treatment,  according  to  Mr.  Kelly's  notes,  was 
a  single  disking,  May  5,  of  plat  Ai  on  the  Hinman  farm  (Table  III.), 
which,  as  shown  by  a  comparison  with  C  i  of  the  same  table,  seems 
to  have  reduced  the  number  of  hills  infested  by  only  sixteen  per 
cent,  for  the  ants  and  seventeen  per  cent,  for  the  aphids,,  and  the 
number  of  insects  by  four  per  cent,  for  the  former  and  fourteen  per 
cent,  for  the  latter.  As  these  plats  were  not  examined  until  May 
31,  that  is  to  say  twenty-six  days  after  the  treatment,  these  figures 
probably  ought  not  to  be  taken  into  account.  It  was  hardly  to  be 
expected  that  the  original  difference  between  check  and  experi- 
mental plats  should  continue  unchanged  during  this  interval  of 
nearly  four  weeks. 

Five  of  the  pairs  of  plats  brought  into  comparison  differed  in  re- 
spect to  treatment  only  by  the  fact  that  the  experimental  plat  was  in 
each  case  treated  with  a  disk  harrow  once  more  than  its  correspond- 
ing check.  If  the  ratios  for  these  five  plats  be  averaged,  it  appears 
that  the  result  of  a  single  disking  in  1905  on  the  Hinman  and  Fin- 
negan  places  may  be  described  in  general  terms  as  reducing  the 
number  of  hills  infested  by  forty-four  per  cent,  for  the  ants  and  fifty- 
one  per  cent,  for  the  aphids,  and  the  number  of  insects  by  fifty-seven 
per  cent,  for  the  ants  and  sixty-three  per  cent,  for  the  aphids.  Or, 
still  more  generally  speaking,  it  may  be  said  that  the  average  effect 
of  a  single  treatment  with  the  disk  harrow  was  to  reduce  the  number 
of  infested  hills  by  a  little  less  than  half,  and  the  number  of  insects 
in  the  field  by  about  two  thirds.  If,  in  view  of  the  doubtful  charac- 
ter of  one  of  these  comparisons  above  mentioned,  in  which  nearly 
four  weeks  intervened  between  the  experimental  operation  and  the 
inspection  of  the  plats,  we  omit  this  case  from  our  calculation,  this 
statement  may  be  revised  to  the  effect  that  a  single  disking  may  be 
expected  to  reduce  the  number  of  infested  hills  by  something  more 
than  half,  and  the  number  of  insects  in  the  field  by  nearly  three 
fourths. 


122  BULLETIN  No.  104.  [October, 

The  effect  of  twice  disking,  as  shown  by  a  comparison  of  C  i 
and  B  i  of  the  Hinman  field  (Table  III.)  was  to  reduce  the  number 
of  infested  hills  by  fifty-nine  per  cent,  for  the  ants  and  seventy-five 
per  cent,  for  the  aphids,  and  the  number  of  insects  by  sixty-five  per 
cent,  and  eighty- four  per  cent,  respectively.  As  these  two  treat- 
ments were  given,  however,  on  the  5th  and  8th  of  May,  and  the 
inspection  was  not  until  twenty-three  days  later,  it  is  probable  that 
the  full  effect  of  this  treatment  does  not  appear  in  this  statement  of 
the  result,  since  there  was  ample  time  for  the  treated  plats  to  become 
restocked  by  both  ants  and  aphids  by  multiplication  and  migration 
and  by  the  establishment  of  new  aphis  colonies  from  winged  parents 
developed  during  this  interval. 

The  general  conclusion  to  be  drawn  from  this  whole  series  of  ex- 
periments is  to  the  effect  that  the  number  of  both  ants  and  aphids 
may  be  readily  controlled  and  the  injuries  to  corn  in  great  measure 
prevented  by  thorough  and  frequent  stirring  of  the  ground  pre- 
vious to  corn  planting,  and  that  the  disk  harrow  or  its  equivalent  is 
much  the  best  implement  for  the  purpose.  Indeed,  the  treatment 
most  effective  for  the  destruction  of  the  root-aphis  and  its  attendant 
ant  in  spring  is  in  great  measure  that  which  will  be  found  most  use- 
ful as  a  thorough  preparation  of  the  soil  for  corn,  the  main  differ- 
ence being  that  a  thorough  overturning  and  stirring  of  the  soil  is 
the  essential  thing  for  the  destruction  of  the  root-louse,  while  it  is 
sufficient  for  the  corn  plant  if  the  earth  be  merely  pulverized  in 
place. 

If  the  corn  farmer  will  prepare  his  old  corn  ground  early  and 
thoroughly,  using  the  plow  and  the  disk  harrow  by  preference,  he 
should  have  little  trouble  in  the  beginning  of  the  season  from  the 
corn  root-aphis,  and  so  fast  and  so  far  as  the  general  community  acts 
in  accordance  with  this  idea,  to  that  extent  will  later  injuries  by  this 
aphis  be  forestalled.  It  is  in  this  as  in  many  other  cases,  one  acting 
by  himself  alone  can  accomplish  relatively  little  even  for  his  own 
protection;  the  welfare  of  each  depends  on  intelligent  cooperation 
by  all. 

It  is  further  to  be  concluded  from  the  observations  here  re- 
ported, that  if  infested  corn  ground  be  planted  to  oats,  the  root-lice 
will  leave  it  or  perish  in  it  (just  which  we  do  not  yet  know)  by 
the  end  of  May.  A  rotation  with  a  short  period  in  corn  must  con- 
sequently act  to  check  the  multiplication  of  this  insect  and  to  dimm- 
ish its  injuries  to  corn. 


1905.1  EXPERIMENTS  ON  CORN' INSECTS.  123 

TABLE  V.    COMPARATIVE  EXHIBIT  OF  RESULTS  OF  TREATMENT. 


Experiment 

Differential  Treatment 

Percentages  of  Reduction 

Ants 

Aphids 

Hills 
in- 
fested 

Number 
of 
insects 

Hills 
in- 
fested 

Number 
of 
insects 

1.  Coolidgre  
2.  Doerr  .  .   

3.  Hinman  
4.  Finnegan  

Disked  three  times,  harrowed  once.. 
Plowed  once,  harrowed  three  times 

64 
60 

58 
52 

33 
59 

92 
68 

90 
63 

42 
65 

82 

75 

64 
72 

41 

75 

92 
81 

89 
81 

43 
84 

Disked  once,  (after  heavy  rains).    .. 
Disked  once,  (after  harrowing  

Disked  once,  (after  previous  disking' 

124  BULLETIN  No.  104.  [October T 


FIELD  EXPERIMENTS  FOR  THE  PROTECTION  OF  CORN 
AGAINST  CHINCH-BUG  INJURY. 

BARRIER  EXPERIMENTS. 

Experiment  of  1895. — In  my  ninth  entomological  report,  pub- 
lished in  1898,  I  gave  an  account,  in  an  article  on  "Midsummer 
Measures  against  the  Chinch-bug,"*  of  a  field  experiment  made  in 

"Twentieth  Rep.  State  Ent.  111.,  pp.  37-44. 

1895  f°r  ^ie  destruction  of  that  insect  as  it  passes  in  June  and  early 
July  from  small  grain  to  corn.  The  measures  used  in  this  experi- 
ment were  a  combination  program  of  a  dusty  furrow  for  the  ar- 
rest and  destruction  of  chinch-bugs  in  dry  weather,  a  coal-tar  line 
with  post-hole  traps  for  use  when  the  ground  is  too  wet  to  pulverize, 
and  kerosene  emulsion  for  the  destruction  of  the  insect  on  the  corn 
itself. 

This  operation,  carried  on  in  Effingham  county  from  June  5  to 
15  by  one  of  my  assistants,  was  highly  successful  in  the  protection 
of  corn  growing  adjacent  to  a  heavily  infested  2O-acre  field  of 
wheat,  approximately  twelve  bushels  of  chinch-bugs  being  destroyed 
in  the  process  at  a  cost  of  less  than  five  dollars  for  the  materials  used. 

Extreme  conditions  prevailed  at  the  time  of  this  experiment. 
Injury  by  chinch-bugs  to  grass,  small  grains,  and  corn  had  contin- 
ued in  this  locality  for  some  years  with  increasing  intensity,  and 
these  insects  had  become  so  numerous  in  the  wheat  that  they  had 
already  destroyed  the  crop  and  virtually  all  other  grass-like  vegeta- 
tion in  the  field  referred  to,  by  the  5th  of  June.  Compelled  to  leave 
the  wheat  to  avoid  starvation,  they  moved  out  of  it  rapidly,  wholly 
deserting  it  within  a  very  few  days.  The  corn  adjacent  was  thus 
exposed  to  immediate  and  complete  destruction  by  the  invading 
horde,  and  would  inevitably  have  been  soon  destroyed  if  active 
measures  had  not  been  taken  to  protect  it,  a  fact  made  perfectly  ap- 
parent by  the  fate  of  other  similarly  situated  fields  in  the  neigh- 
borhood. 

The  weather  of  the  season  had  been  very  dry,  and  it  was  in- 
tensely hot,  conditions  which,  although  unfavorable  to  the  infested 
crops,  were  unusually  favorable  to  the  easy  success  of  measures  for 
the  destruction  of  the  chinch-bugs.  A  dusty  furrow,  readily  made 
and  maintained  between  the  wheat  and  the  corn,  trapped  the  in- 
sects in  myriads  as  they  attempted  to  pass  from  one  field  to  the 
other,  and  the  heat  of  the  dry  dust  in  the  bottom  of  the  furrow, 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  125 

fully  exposed  to  the  sun,  speedily  killed  them.  The  coal-tar  barrier 
was,  in  fact,  required  but  once,  and  the  kerosene  emulsion  was  used 
only  to  destroy  the  bugs  which  had  entered  the  field  before  the 
experiment  began  and  a  few  which  escaped  into  it  in  an  interval  be- 
tween a  shower  of  rain  and  the  establishment  of  the  tar  line.  As  the 
protected  field  of  corn  bore  a  good  crop  while  other  fields  in  the 
neighborhood  were  almost  wholly  destroyed,  the  demonstration  of 
the  usefulness  of  this  method  was  complete  for  these  extreme  con- 
ditions. 

Experiments  of  1904. — Wishing  to  know,  however,  what  might 
be  done  by  similar  operations  under  more  ordinary  circumstances, 
especially  when  a  chinch-bug  outbreak  was  but  just  beginning  and 
when  the  weather  was  generally  unfavorable  to  success,  I  prepared 
in  the  spring  of  1904  for  several  field  trials,  to  be  made  at  different 
places  in  southern  Illinois  where  a  previous  inspection  had  shown 
that  the  chinch-bugs  were  present  in  numbers  sufficient  to  threaten 
more  or  less  injury  to  wheat  and  corn.  The  fields  selected  were  in 
four  localities:  near  Carbondale,  in  Jackson  county;  near  Dubois, 
in  Washington  county ;  and  near  Fairman  and  Odin  respectively,  in 
Marion  county. 

The  experiment  was  placed  in  charge  of  Mr.  E.  P.  Taylor,  and 
I  owe  the  results  here  reported  to  his  energy  and  faithfulness  in  the 
field,  and  to  the  fulness  and  exactness  of  his  notes. 

Although  the  prospect  of  insect  injury  was  considerable  at  all 
these  places  in  the  early  part  of  the  year,  the  weather  of  the  spring 
and  early  summer  was  so  wet  and  much  of  the  time  so  cool  that  the 
multiplication  of  the  insects  was  in  great  measure  prevented,  and 
they  finally  became  abundant  enough  to  injure  corn  seriously  only  in 
the  Carbondale  neighborhood.  The  whole  experiment  was  faith- 
fully carried  through,  however,  at  all  the  above  places,  and  with  use- 
ful results  at  each. 

At  Carbondale,  rain  fell  twelve  times  and  on  eleven  different  days 
between  June  24  and  July  25,  and  the  ground  was  kept  so  moist 
by  rains  at  all  the  places  mentioned  that  the  dusty  furrow  could  not 
be  long  maintained  at  any  of  them.  As  a  consequence,  the  tar  line, 
with  post-hole  traps,  was  used  throughout,  and  kerosene  emulsion 
was  only  occasionally  applied,  as  found  necessary. 

The  tar  lines  laid  at  these  various  places  aggregated  more 
than  a  mile  and  a  half  in  length  (508  rods,  exactly),  and  were  main- 
tained for  periods  varying  from  eleven  to  twenty-eight  days,  the 
total  of  this  procedure  being  equivalent  to  the  maintenance  of  an 
effective  coal-tar  barrier  a  mile  in  length  for  twenty-seven  days. 
Post-holes  were  dug  from  one  to  two  feet  deep  at  a  usual  distance  of 


126  BULLETIN  No.  104.  [October, 

twenty  feet  apart  along  all  these  lines;  and  besides  the  continuous 
coal-tar  strip,  diagonal  leaders  about  a  foot  in  length  were  laid  from 
each  hole  outwards  in  two  directions,  as  shown  in  the  accompany- 
ing diagram  (Fig.  2,  p.  131). 

SUMMARY  OF  CONCLUSIONS. 

As  a  general  outcome  of  the  work  at  these  various  places,  it 
was  demonstrated  that  an  effective  barrier  against  the  movement 
of  chinch-bugs  may  be  maintained  for  four  weeks  with  coal-tar, 
poured  along  a  strip  of  ground  properly  prepared,  at  a  cost  for 
materials  of  seven  cents  a  rod,  or  $22.40  a  mile,  and  that  virtually 
all  the  bugs  approaching  these  lines  may  be  trapped  and  killed  in 
post-holes  properly  placed  for  the  purpose. 

The  time  for  which  this  barrier  must  be  kept  intact  will  vary 
from  ten  days,  the  period  found  necessary  in  the  very  dry  weather 
of  1896,  to  thirty  days,  as  required  this  year.  The  labor  necessi- 
tated is  that  of  raising  a  ridge  by  plowing  a  back  furrow  between 
the  infested  field  and  the  one  to  be  protected,  smoothing  and  packing 
this  strip  with  a  light  roller  or  by  hand,  digging  a  row  of  post-holes 
at  intervals  of  about  twenty  feet,  and  laying  the  lines  of  tar  by  pour- 
ing it  upon  the  ground  from  a  can  with  a  tubular  spout.  This  line 
was  renewed  whenever  it  became  dry  or  hard  in  the  sun,  or  when  it 
was  covered  with  dust  in  windy  weather  or  washed  away  or  cov- 
ered with  mud  by  rains.  It  was  necessary  to  pour  fresh  tar  along 
the  line  from  one  to  three  times  a  day,  the  average  at  all  places  for 
the  month  being  three  renewals  every  two  days. 

USE  OF  KEROSENE  EMULSION. 

Where  chinch-bugs  had  entered  corn  before  the  experiment  was 
begun,  and  where,  through  accident  or  mismanagement,  they  es- 
caped across  the  barrier,  they  were  effectively  treated  with  a  four 
per  cent,  kerosene  emulsion.  It  was  shown  that  a  mixture  suffi- 
ciently complete  and  lasting  for  the  purpose  could  easily  be  made 
by  stirring  the  kerosene  and  the  soap  solution  together  with  a  stick 
or  paddle,  and  that  this  emulsion  could  be  conveniently  applied  by 
sprinkling  or  throwing  it  on  the  infested  plants  with  a  whisk-broom, 
or  even  with  the  bare  hand.  Thus  prepared  and  used,  the  four 
per  cent,  emulsion  was  as  strong  as  the  corn  would  stand  without 
some  injury,  and  was  sufficient  to  kill  all  the  chinch-bugs  which  it 
touched. 

The  only  notable  failure  of  this  method  to  destroy  the  chinch- 
bugs  against  which  it  was  used,  occurred  where  the  infestation  of 


1905.1  EXPERIMENTS  ON  CORN  INSECTS.  127 

the  wheat  field  was  slight,  and  where  so  many  grass-like  weeds  had 
sprung  up  in  the  wheat  that  they  afforded  food  to  the  bugs  in  the 
field  at  harvest  sufficient  to  detain  them  there  for  several  days.  There 
was  virtually  no  migration  on  foot  out  of  this  field,  the  chinch-bugs 
generally  lingering  until  the  appearance  of  their  wings  enabled  them 
to  scatter  by  flight  to  more  favorable  breeding  grounds. 

At  Carbondale,  where  they  were  the  most  abundant,  the  corn  ad- 
jacent to  infested  wheat  was  saved  from  all  injury  worth  noticing, 
while  the  crop  on  some  other  fields  in  that  region  ifot  protected, 
was  completely  destroyed  for  many  rods  inward  from  the  edge  of 
the  field,  and  badly  injured  for  a  considerable  distance  further. 

The  Carbondale  Experiment. — On  a  farm  situated  one  mile  west 
of  Carbondale,  belonging  to  Mr.  Robert  Thorpe  and  referred  to 
in  this  account  as  the  Thorpe  farm,  was  an  irregularly  shaped  field 
of  one  hundred  and  forty  acres  of  wheat  which  in  June,  1904,  was 
generally  and  considerably  infested  by  chinch-bugs,*  sufficiently  so 
to  threaten  notable  injury  to  the  wheat  crop  itself  and  the  destruc- 
tion at  harvest-time  of  much  of  the  corn  adjacent.  Indeed,  by  the 
last  week  in  June  the  wheat  was  ripening  irregularly,  turning 
brown  in  patches  where  the  chinch-bug  was  most  abundant,  in  ad- 
vance of  the  general  ripening  of  the  field,  and  from  these  patches 
the  insects  were  already  beginning  to  move  into  other  crops. 

A  corn  field  of  twenty-seven  acres  cornered  into  this  wheat  at 
the  northwest  in  such  a  way  that  the  division  line  of  the  two  crops 
measured  three  hundred  and  seventeen  yards  on  the  east  and  three 
hundred  and  thirty-eight  yards  on  the  south,  the  remainder  of  the 
southern  side  being  bounded  by  woodland.  In  the  southwest  cor- 
ner of  this  wheat  was  another  field  of  corn  of  only  four  acres,  so 
placed  that  it  was  bounded  by  infested  wheat  only  on  one  side  for 
about  one  hundred  yards.  A  third  field  of  corn,  on  an  adjacent  farm 
belonging  to  Ralph  Thompson,  was  also  exposed  to  invasion  from 
the  wheat  field  for  a  distance  of  about  one  hundred  and  forty  yards. 
This  corn  was  south  of  the  wheat,  from  which  it  was  separated  by 
a  roadway  of  the  usual  width. 

The  situation  here  was  complicated  by  the  fact  that  in  the  north- 
west field  of  twenty-seven  acres  of  corn  a  large  pile  of  waste  from 
a  corn  shredder  had  been  left  the  preceding  fall,  in  which  quantities 
of  chinch-bugs  had  passed  the  winter.  Coming  out  in  spring,  many 
of  these  laid  their  eggs  in  the  young  corn,  which  thus  became  im- 
mediately infested  from  within  by  the  first  generation  of  the  year. 
A  part  of  the  wheat  bordering  this  field  on  the  south  had  ripened 
early,  owing  perhaps  to  chinch-bug  injury,  and  the  bugs  from  this 
vicinity  had  already  begun  to  invade  the  corn  before  our  experiment 


128  BULLETIN  No.  104.  [October, 

was  begun,  infesting  a  strip  about  thirty  yards  in  length  and  seven 
or  eight  rows  deep. 

To  prevent  the  further  entrance  of  chinch-bugs  into  these  three 
corn  fields  from  without,  1080  yards  (about  three  fifths  of  a  mile) 
of  impassable  barriers  were  required,  with  approximately  160 
post-hole  traps  distributed  along  them ;  and  to  destroy  those  already 
in  the  field  before  our  work  began  it  was  necessary  to  spray  a  part 
of  the  northwest  field  with  kerosene  emulsion. 

When  the*se  premises  were  taken  in  charge  for  our  purpose  by 
Mr.  Taylor,  June  23,  1904,  the  wheat  was  already  nearly  ripe,  and 
harvesting  began  a  few  days  later,  continuing  until  July  7.  The 
chinch-bugs  were  at  first  by  no  means  hurried  in  their  movement 
out  of  the  wheat,  as  there  were  still  grassy  weeds  in  the  stubble  to 
detain  them,  and  the  frequent  showers  of  the  following  month  kept 
this  vegetation  in  good  condition  continuously.  The  movement 
towards  the  corn  was  well  marked,  however,  from  the  beginning,  and 
prompt  measures  were  necessary  to  protect  that  crop.  There  was 
also  urgent  need  for  a  destruction  of  chinch-bugs  already  in  the 
corn,  and  this  was  the  first  task  undertaken,  kerosene  emulsion  being 
made  up  to  June  23  in  a  rather  rough-and-ready  manner  by  stirring 
the  kerosene  and  soap-suds  together  vigorously  for  several  minutes 
with  a  stick.  This  mixture  was  then  flirted  on  to  the  corn  with  the 
naked  hand  at  a  rate  of  about  a  pint  to  every  three  hills.  The  first 
mixture  contained  five  per  cent,  of  kerosene,  and  was  evidently  too 
crudely  made,  proving  injurious  to  the  corn,  especially  where  it  was 
held  in  the  conical  cavity  formed  by  the  terminal  tuft  of  leaves.  It 
was  estimated  that  about  twenty-five  per  cent,  of  the  stalks  treated 
on  this  first  date  were  damaged  more  or  less.  A  four  per  cent,  mix- 
ture, on  the  other  hand,  as  applied  on  the  24th  of  June,  did  no  dam- 
age to  the  plants,  and  is  reported  to  have  killed  the  chinch-bugs  as 
soon  as  it  touched  them.  This  emulsion  was  used  from  time  to 
time  thoroughout  the  whole  period  of  the  experiment  in  parts  of 
two  fields  of  corn  where  the  bugs  made  their  way  around  the  ends 
of  the  barriers  in  number  to  require  special  measures  for  their  de- 
struction. 

An  effort  was  made  at  the  very  first  to  use  a  dusty  furrow  as  a 
barrier,  with  post-holes  dug  in  the  bottom  to  trap  the  bugs,  and 
about  one  hundred  and  sixty  rods  of  such  furrows  were  made  June 
23  to  25  on  the  eastern  and  southern  sides  of  the  northwest  field, 
and  on  the  west  side  of  the  four-acre  patch.  The  ground  was  deeply 
plowed  and  thoroughly  harrowed  in  a  four-foot  strip,  and  a  ridge 
was  formed  by  making  a  back  furrow  down  the  middle.  A  log  was 
then  dragged  through  the  center  of  the  strip  until  a  dusty  groove 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  129 

or  furrow  was  made  several  inches  in  depth.  In  the  bottom  of  this 
holes  were  dug  with  an  ordinary  post-hole  digger  at  intervals  of 
twenty  feet.  The  ground  was  too  damp,  however,  even  at  first, 
to  make  a  satisfactory  barrier,  and  heavy  rains  falling  on  the  24th 
and  25th  of  June  compelled  a  prompt  abandonment  of  this  part 
of  the  operation. 

Coal-tar  lines,  substituted  for  the  furrow  because  of  the  weathei , 
were  laid  on  the  24th  to  the  26th  so  far  as  needed  to  protect  fields 
of  corn  on  the  Thorpe  farm.  June  30  it  became  necessary  to  lay 
also  a  similar  line  for  a  short  distance  along  the  border  of  the  south 
field  on  the  Thompson  farm,  as  the  hungry  bugs  were  at  this  time 
crossing  the  road  in  large  numbers  on  their  way  to  the  corn.  All 
these  tar  lines  aggregated  about  two  hundred  rods  in  length,  and 
were  maintained  in  an  effective  condition  around  the  different  fields 
from  eighteen  to  twenty-eight  days.  It  was  necessary  to  renew 
them,  on  an  average,  twice  every  three  days.  One  hundred  and 
forty-five  gallons  of  tar  were  used  in  all,  at  a  cost  of  $8.85.  The 
supply  of  tar  being  temporarily  exhausted  July  9,  kerosene  was 
poured  along  the  dried-out  line  on  the  ground,  with  the  effect  to 
soften  it  and  to  keep  it  soft  for  thirty  hours.  Besides  the  hardening 
of  the  tar  by  exposure  to  the  sun,  the  barriers  were  occasionally 
bridged  by  dust  blown  into  them,  and  broken  by  rains  which  some- 
times washed  them  away  in  spots  or  covered  parts  of  them  with  mud. 

It  is  needless  to  say  that  no  chinch-bugs  crossed  the  tar  line  as 
long  as  it  was  kept  reasonably  fresh.  The  post-hole  traps,  into  which 
the  bugs  were  led  by  diagonal  lines  or  leaders  of  tar,  worked  effect- 
ively, and  bugs  accumulated  in  them  in  variable,  amounts  up  to  a 
quart  for  each  hole.  Here  they  were  readily  killed  by  pouring  a 
little  tar-water  or  kerosene  upon  them. 

The  movement  of  the  bugs  was  greajtly  influenced  by  the 
weather.  On  warm  and  sunny  days  they  sometimes  began  to  travel 
not  long  after  sunrise  and  continued  until  near  sunset,  but  in  cool 
and  cloudy  weather  they  moved  later  or  not  at  all,  and  the  traps  con- 
sequently caught  few  or  none.  Whatever  the  weather,  they  never 
traveled  at  night.  July  i  to  5,  when  the  last  of  the  wheat  was  being 
cut,  they  left  the  field  more  rapidly,  and  more  of  them  were  then 
destroyed  than  at  any  other  time.  By  the  24th  of  July  the  move- 
ment was  practically  over,  most  of  the  bugs  remaining  having  fin- 
ished their  growth  and  got  their  wings.  Many  of  them  had  but 
recently  transformed,  as  shown  by  their  paler  color,  and  pairing 
for  the  next  generation  was  actively  in  progress. 

The  final  result  of  the  above  operation  is  given  in  Mr.  Taylor's 
report  of  conditions  July  30,  at  which  time  he  says  that  "all  the 


130  BULLETIN  No.  104.  [October, 

fields  of  corn  which  have  received  the  protection  of  our  barriers  are 
quite  uninjured  and  practically  free  from  chinch-bugs."  The  small 
sprinkling  of  the  insects  to  be  found  in  any  of  the  fields  had  doubt- 
less flown  in  as  they  reached  maturity.  The  actual  cost  for  coal- 
tar  was  $8.85,  and  for  kerosene  and  soap  it  was  $2.55.  The  labor 
necessary  to  the  operation  was  28  days'  work  of  a  man  and  2 
of  a  team,  the  latter  for  making  the  back  furrow,  for  rolling  the 
ground,  and  for  hauling  the  tar  and  kerosene  emulsion  to  the  field. 

It  should  be  noticed  that  this  defensive  operation  was  as  com- 
plete and  as  expensive  as  would  have  been  necessary  if  the  chinch- 
bugs  had  been  ten  times  as  numerous  in  the  wheat.  That  is,  the 
labor  and  cost  would  have  been  no  greater  to  protect  the  corn  against 
the  danger  of  a  loss  ten  times  as  great  as  it  would  have  suffered  if 
the  bugs  actually  in  the  wheat  this  year  had  been  allowed  to  go  their 
way. 

The  Fairman  Experiment. — Near  Fairman,  in  Marion  county, 
a  large  field  of  wheat  on  the  farm  of  Mr.  Wm.  Meredith,  moderately 
infested  by  chinch-bugs,  was  selected  for  experiment.  This  field 
was  bordered  for  eighty  rods  by  a  field  of  corn,  from  which  it  was 
separated  by  a  wire  fence.  Operations  were  begun  here  June  30, 
when  the  wheat  was  already  ripe,  harvesting  being  in  progress  at 
the  side  of  the  field  farthest  from  the  corn.  To  protect  the  latter 
crop  a  double  barrier  was  made  within  the  margin  of  the  wheat 
field,  where  two  swathes  of  the  grain  were  cut  to  give  room  for 
the  operation. 

A  strip  five  feet  wide  the  whole  length  of  the  field  was  plowed 
and  thoroughly  pulverized,  and  a  deep  dusty  furrow  was  then  made 
in  the  middle  of  it ;  and  a  strip  two  feet  outside  this  was  also  pre- 
pared for  the  tar  line,  various  parts  of  it  by  different  methods. 

Preparation  of  the  Dusty  Furrow. — Although  wet  weather  pre- 
vented the  continuous  use  of  the  dusty  furrow  as  a  barrier  to  the 
movement  of  the  chinch-bugs,  and  compelled  a  reliance  on  the  coal- 
tar  line  instead,  the  method  used  in  preparing  the  former  is  well 
worthy  of  description.  First,  a  furrow  was  plowed  about  seven 
inches  deep  and  fourteen  inches  wide  the  whole  length  of  the  field  in 
the  center  of  the  stubble  border.  On  the  return  a  second  furrow 
was  made  immediately  beside  the  first,  the  dirt  from  which  was 
thrown  back  into  the  first  furrow,  leaving  no  unplowed  earth  be- 
tween them.  The  land  was  then  widened  by  plowing  back  and  forth, 
throwing  the  earth  toward  the  center  each  time,  until  six  furrows 
had  been  made.  This  strip,  about  six  feet  wide,  was  then  harrowed 
ten  times  with  a  common  disk  harrow,  and  twice  with  a  straight- 
toothed  harrow,  leaving  the  ground  level,  thoroughly  pulverized, 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  131 

and  free  from  clods  and  weeds.  Next,  near  the  center  of  this  pul- 
verized strip  a  deep  dead  furrow  was  made  by  plowing  twice  back 
and  forth  in  the  same  line, — once  in  each  direction  with  an  ordinary 
fourteen-inch  plow  and  once  with  a  small  diamond  plow, — and  in 
the  ditch  so  made,  a  log  eight  feet  long  and  eight  inches  through  was 
dragged  by  a  single  horse  (a  mule  would  have  been  better)  until  the 
sides  of  the  ditch  were  pulverized  to  the  finest  dust.  This  work 
would  require,  for  an  eighty-rod  line,  the  labor  of  two  men  and  a 
team  for  a  little  more  than  half  a  day.  The  average  cost  of  a  dusty 
furrow  constructed  as  above  described,  would  be  practically  three 
cents  a  rod,  as  shown  by  the  actual  labor  of  man  and  horse  used  on 
this  eighty-rod  line. 

This  furrow  was  finished  July  3,  and  caught  and  held  the  chinch- 
bugs  generally  during  that  day  and  the  following ;  but  July  5  a  heavy 
rain  fell  which  put  it  out  of  service,  and  even  the  following  day  the 
ground  was  too  wet  to  renew  it  by  dragging  again  with  the  log. 
Equally  heavy  rains  falling  on  the  8th  and  on  the  nth  discouraged 
further  work  with  it,  and  it  was  practically  abandoned  in  favor  of 
the  tar  line. 

When  in  use,  some  method  of  destroying  the  bugs  entrapped  is 
necessary.  In  bright  summer  weather  the  dust  in  the  bottom  be- 
comes so  hot  as  to  kill  all  the  chinch-bugs  except  those  with  wings, 
and  many  of  these  also  will  succumb.  Otherwise,  shallow  pits  may 
be  dug  with  a  post-hole  digger  or  spade  at  intervals  in  the  bottom  of 
the  furrow,  care  being  taken  to  restore  the  dusty  surfaces  disturbed 
in  this  operation.  The  harassed  bugs  will  accumulate  here  in  quan- 
tities, and  may  be  killed  by  pouring  a  little  kerosene  upon  them. 
Experiments  described  on  another  page  of  this  report  indicate  that 
the  bugs  caught  in  the  dusty  ditch  may  also  be  quickly  killed  by  a 
brief  exposure  to  a  kerosene  spray  or  to  the  flame  of  a  gasoline 
torch. 

DIAGRAM  OF  CHINCH  BUG  BARRIER 


i  Hol.Tr«p(Di«i»8in) 
t  Hole  Trap  Li  ne 


1     Spac?e          Betlween       Tkr         Line  *        and       piusty      Furt-ow 


Infested    Wlieat 

Fig.  2.    Dusty  furrow,  and  coal-tar  line,  with  post-hole  traps  and  diagonal  ''leaders"  of  tar. 

Preparation  of  the  Coal-tar  Line. — To  receive  the  tar  line  it  is 
necessary  to  have  a  smooth  hard  band  of  earth  like  a  well-beaten 
path,  into  which  the  tar  will  not  readily  sink.  This  should  be  about 


132  BULLETIN  No.  104.  {October, 

level  with  the  adjacent  surface  or  a  little  above,  as  otherwise  the 
line  is  likely  to  be  bridged  by  dust  and  rubbish  blown  upon  it.  The 
effectiveness  of  the  barrier  depends,  indeed,  largely  upon  the  prep- 
aration of  the  strip  of  earth  along  which  the  tar  is  to  be  poured. 
Such  a  path  was  prepared  in  six  different  ways  on  as  many  sections 
of  the  line. 

Beginning  at  one  end,  a  strip  ten  rods  long  was  prepared  beside 
the  fence  by  simply  scraping  smooth  with  a  hoe  and  sharp  spade. 
Where  the  ground  is  hard,  and  grass  and  weeds  form  a  thick  mat, 
one  man  will  not  ordinarily  clear  over  five  rods  an  hour.  This 
method  is  laborious  and  expensive,  and  would  only  be  necessary 
where  a  team  could  not  be  used.  It  would  cost  for  labor  about  two 
cents  a  rod. 

The  second  section  of  ten  rods  was  prepared  by  plowing  two 
very  shallow  furrows  with  a  fourteen-inch  plow,  merely  skimming 
away  the  weeds,  grass,  and  surface  roots.  Both  these  furrows 
threw  the  dirt  towards  the  wheat  field,  leaving  a  belt  about  two 
feet  wide  free  from  weeds  and  grass,  and  separated  from  the  wheat 
by  the  dirt  thrown  over.  The  work  was  thus  done  rapidly,  but  by 
this  method  the  bare  strip  is  left  lower  than  the  general  surface  and 
is  liable  to  be  covered  in  places  with  dust  and  weeds  by  the  wind. 
It  must  also  be  smoothed  here  and  there  with  .a  -hoe  before  the  tar 
is  laid  down.  Eighty  rods  can  be  prepared  in  this  way  by  one  man 
and  a  single  horse  in  half  a  day. 

The  third  section  of  ten  rods  was  made  ready  by  plowing  a 
back  furrow  in  the  stubble  and  beating  the  ridge  of  earth  flat  and 
hard  with  spades.  This  was  one  of  the  most  satisfactory  of  the 
methods  used,  as  by  it  the  tar  line  is  placed  on  a  ridge  where  it  is 
not  likely  to  be  bridged  either  by  winds  or  rains.  The  comparatively 
loose  earth  will  at  first  absorb  the  tar  more  freely  than  the  hard  bot- 
tom of  a  furrow,  but  this  difference  is  not  noticeable  after  a  few 
days.  A  ridge  of  this  kind  may  be  more  rapidly  prepared  by  using 
an  inverted  trough-like  drag  of  planks,  weighted  if  necessary,  to 
compact  the  earth,  as  has  been  done  in  Kansas  on  a  large  scale. 
This  will  take,  for  an  eighty-rod  line,  the  work  of  a  man  and  team 
for  about  half  a  day. 

The  fourth  ten-rod  section  was  prepared  by  plowing  a  very  shal- 
low furrow  with  a  single  horse  along  the  edge  of  the  grass  in  the 
headland  next  the  fence,  throwing  the  dirt  upon  the  stubble.  This 
was  not  a  satisfactory  operation,  however,  as  it  left  too  narrow 
a  smooth  surface. 

The  fifth  section,  forty  rods  in  length,  was  prepared  by  simply 
scraping  away  the  weed  and  grass  roots  as  clean  as  possible  with  an 


W05.}  EXPERIMENTS  ON  CORN  INSECTS.  133 

ordinary  farm  scraper,  making  a  strip  about  two  feet  wide,  one  or 
two  inches  below  the  general  level.  It  was  necessary,  however,  to 
scrape  the  surface  afterwards  with  a  shovel  or  hoe,  as  many  irreg- 
ularities were  otherwise  left  to  carry  the  tar  in  all  directions.  The 
labor  of  a  man  and  team  for  half  a  day  would  be  required  to  pre- 
pare eighty  rods  in  this  way. 

Finally,  the  sixth  section,  eighteen  rods  long,  was  made  in 
meadow  land  by  plowing  two  shallow  furrows,  throwing  the  dirt 
outward  in  a  way  to  leave  a  level  dead  furrow  about  two  feet  wide, 
and  smoothing  and  leveling  the  bottom  more  exactly  by  hand. 
This  is  a  rapid  and  satisfactory  method  of  preparation  where  a 
barrier  can  be  made  in  sod  with  room  to  work  a  team. 

The  tar  line  was  made  by  pouring  from  a  watering  can  a  slender 
stream  of  tar  continuously  along  the  ground.  Holes  were  then  dug 
with  an  ordinary  post-hole  digger  to  a  depth  of  about  a  foot  and  at 
a  distance  of  twenty  feet  apart.  They  were  placed  on  the  stubble 
side  of  the  line,  and  short  diagonal  lines  of  tar  were  laid  from  each 
hole  to  the  right  and  left  in  a  way  to  conduct  chinch-bugs  approach- 
ing the  line  to  the  hole  itself.  Six  gallons  of  tar  were  needed  to 
construct  this  barrier  along  the  eighty-rod  boundary.  During  the 
period  of  twelve  days  covered  by  this  experiment,  the  tar  line  was 
renewed  eighteen  times  in  all,  as  many  as  three  times  a  day  at  first, 
while  every  other  day  was  sufficient  towards  the  end  of  the  period. 
Fifty-five  gallons  of  tar  were  used  in  these  eighteen  operations, 
an  average  of  three  gallons  for  each  time.  The  cost  of  the  tar  for 
this  period  was  $2.40,  or  twenty  cents  a  day  for  the  twelve  days. 
This  line  was  of  course  effective  from  the  first,  and  bugs  were 
continuously  caught  in  the  holes  along  it,  where  they  were  easily 
killed  with  tar-water  or  kerosene. 

Dubois  and  Odin  Experiments. — At  Dubois,  in  Washington 
county,  an  irregular  field  of  corn  containing  twenty-eight  acres  was 
protected  from  invasion  by  chinch-bugs  from  two  fields  of  wheat 
adjoining  it.  On  the  east  side  along  a  boundary  line  of  two  hun- 
dred and  fifty  yards  a  double  barrier  was  constructed,  a  furrow  next 
the  corn  and  a  tar  line  with  post-holes  immediately  outside.  To  the 
west  and  north  a  tar  line  was  laid  seven  hundred  and  sixteen  rods 
in  length,  and  post-holes  were  dug  every  twenty  feet.  Although 
the  chinch-bugs  proved  not  to  be  sufficiently  numerous  in  the  wheat 
to  have  caused  any  great  injury  even  if  they  had  escaped  into  the 
corn  without  hindrance,  these  barriers  were  as  carefully  maintained 
for  eleven  days,  from  June  29  to  July  10,  as  if  the  salvation  of  the 
corn  depended  upon  their  efficiency. 


134  BULLETIN  No.  104.  [October, 

At  Odin  was  a  small  field  of  infested  wheat,  containing  four 
acres,  with  corn  bordering  it  to  the  north  and  west.  A  tar  and  post- 
hole  line  was  carried  along  these  two  sides  for  about  a  thousand 
feet  to  prevent  the  passage  of  the  bugs  across  the  boundaries. 

The  conditions  and  results  at  both  these  places  were  so  similar 
to  those  at  Fairman  that  no  detailed  account  is  necessary.  At  Odin 
a  simple  method  was  made  use  of  for  preparing  the  ground  for  the 
tar.  A  heavy  plank  was  dragged  endwise  back  and  forth  about  ten 
times  along  the  edge  of  the  wheat,  thus  smoothing  and  packing  well 
a  strip  two  feet  wide.  With  a  short-handled  shovel  the  ground  was 
then  packed  and  pounded  to  a  hard  surface,  in  which  a  narrow  and 
shallow  groove  was  made  with  the  shovel  handle  for  the  reception 
of  the  tar.  This  was  poured  in  a  stream  the  size  of  a  lead-pencil 
from  the  spout  of  a  watering-pot  from  which  the  sprinkler  had  been 
removed.  The  line  so  laid  spread  out  on  the  ground  to  a  width  of  a 
half  to  three  quarters  of  an  inch. 

EXPERIMENTS  WITH  FLUID  INSECTICIDES. 

In  my  first  report,  the  twelfth  of  this  office,  published  in  1883, 
is  a  description  of  the  first  attempts  made  to  destroy  chinch-bugs 
by  means  of  kerosene  mixtures.  In  the  operation  there  reported, 
nineteen  experiments  were  made,  mainly  with  emulsions  varying  in 
strength  from  two  and  a  half  to  six  and  two  thirds  per  cent,  of  kero- 
sene, but  partly  with  mechanical  mixtures  of  the  crudest  kind. 

These  insecticide  fluids  were  sprinkled  upon  infested  hills  of  corn 
during  the  last  days  of  July,  partly  transplanted  hills  which  had  been 
removed  to  my  office  laboratory  and  partly  hills  in  the  field  isolated 
by  surrounding  them  with  barriers  of  boards  and  coal-tar  impassable 
to  insects  on  foot.  Proper  checks  were  kept  in  all  cases  of  hills 
treated  precisely  like  those  under  experiment  except  that  plain  water 
was  substituted  for  the  fluid  insecticides.  A  single  additional  experi- 
ment was  made  with  strong  soap-suds  to  which  no  kerosene  had 
been  added. 

The  general  result  of  a  single  application  of  any  of  these  mix- 
tures was  the  destruction  of  about  eighty  per  cent,  of  the  bugs  on 
the  corn  at  the  time,  the  remaining  twenty  per  cent,  being  either 
protected  by  their  position  from  contact  with  the  insecticides  or  re- 
viving after  a  time  without  noticeable  injury.  Most  of  the  escaping 
specimens  were  apparently  on  the  ground  under  clods  of  earth 
when  the  corn  was  treated. 

Frequent  use  has  since  been  made  of  the  kerosene  mixtures  in 
field  experiments  by  ourselves  and  by  other  entomologists,  partic- 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  135 

ularly  for  the  destruction  of  chinch-bugs  accumulating  on  the  outer 
rows  of  corn  as  they  move  into  the  fields  from  wheat  or  oats  at 
harvest-time.  This  insecticide  method,  however,  is  mainly  useful  as 
an  adjunct  to  the  barrier  method  already  described. 

With  a  view  to  testing  this  operation  on  a  comparatively  large 
scale,  I  instructed  Mr.  E.  P.  Taylor,  in  charge  of  my  field  operations 
against  the  chinch-bug  in  1904,  to  prepare  and  apply  kerosene 
emulsion  in  the  field  wherever  necessary  and  practicable  in  his  oper- 
ations, to  keep  an  account  of  labor  required  and  the  cost  of  materi- 
als, and  to  observe  critically  and  report  the  effects  of  the  treatment 
upon  both  insects  and  plants.  Experiments  of  this  kind  were  made 
in  early  July  of  that  year  with  both  kerosene  emulsion  and  whale- 
oil  soap. 

In  the  absence  of  a  mixing  pump,  the  kerosene  and  soap-suds, 
two  parts  of  the  first  to  one  of  the  second,  were  thoroughly  mixed  by 
a  simple  violent  beating  with  a  stick  for  about  five  minutes,  the  ves- 
sels containing  the  fluids  being  covered  with  a  cloth  to  prevent  spat- 
tering. Emulsions  so  prepared,  although  doubtless  not  so  perfect 
as  could  be  made  with  a  pump,  were  in  every  way  sufficient  for  the 
purpose,  standing  for  at  least  two  hours  without  any  appearance  of 
a  separation  of  the  oil  and  water,  and  doing  no  damage  whatever 
to  the  corn  if  diluted  to  contain  four  per  cent,  of  kerosene.  If  more 
than  this  proportion  of  the  oil  were  used,  injury  to  the  plant  was 
likely  to  result,  especially  if  the  upper  leaves  were  treated. 

Details  of  Field  Experiments. — At  Fairman,  July  4,  one  fifth  of 
an  acre  of  corn  was  sprayed  with  a  kerosene  emulsion  prepared  as 
above  and  diluted  to  contain  four  per  cent,  of  kerosene.  No  ap- 
paratus was  used  in  making  the  application,  but  the  fluid  was  sim- 
ply flirted  upon  the  corn  by  hand.  Ten  gallons  of  the  mixture  were 
used  in  this  treatment,  equivalent  to  about  a  barrel  (fifty  gallons) 
per  acre,  or  approximately  one  and  two  thirds  ounces  per  hill.  The 
amount  of  kerosene  in  a  four  per  cent,  mixture  used  at  this  rate 
would  be  two  gallons  per  acre  of  corn  treated. 

Twenty-four  hours  later  none  of  the  plants  showed  signs  of 
injury,  and  great  numbers  of  the  bugs  were  dead  upon  the  ground 
and  in  the  cups  at  the  bases  of  the  leaves.  Living  chinch-bugs 
enough  remained  in  this  part  of  the  field  to  extend  their  attack 
graduallv  inwards,  until  by  July  9,  five  days  after  treatment,  they 
were  to  be  found  in  small  numbers  ten  rods  beyond  the  area  infested 
at  first.  The  number  remaining,  however,  was  economically  in- 
significant, since  no  injury  to  the  corn  could  have  resulted. 

A  second  treatment  was  applied  July  12  to  this  whole  area,  now 
about  three  fourths  of  an  acre  in  all,  twenty-four  gallons  of  the 


136  BULLETIN  No.  104.  [October, 

mixture  being  used.  A  part  of  the  corn  was  now  about  two  and  a 
half  feet  high,  and  the  chinch-bugs  were  mainly  behind  the  leaf- 
sheaths  or  within  the  cpnical  cavity  at  the  tip  of  the  plant.  The 
kerosene  mixture  was  applied  in  part  by  hand  as  before,  and  in  part 
by  pouring  from  a  common  sprinkling  can,  but  the  former  method 
was  found  the  more  rapid  and  also  the  more  economical  of  material. 

As  shown  by  examination  the  following  day,  not  a  plant  was  in- 
jured by  this  treatment,  and  only  a  few  bugs  were  left  alive,  mainly 
on  plants  with  leaves  so  rolled  and  curled  as  to  protect  the  bugs 
within  them.  A  careful  count  was  made  of  all  the  bugs,  living  and 
dead,  found  upon  ten  average  hills,  including  those  on  the  ground 
about  the  bases  of  the  plants,  with  the  result  that  eighty-eight  per 
cent,  of  all  found  were  dead.  An  additional  treatment  was  given  to 
the  corn  still  infested,  and  July  24  the  owner  of  the  field,  after  a 
careful  examination,  found  an  average  of  twenty  to  twenty-five  liv- 
ing bugs  per  hill.  The  corn  was  at  this  time  beginning  to  tassel.  The 
same  treatment,  would,  of  course,  have  destroyed  any  number  of 
chinch-bugs  with  which  the  corn  might  have  been  infested.  As  the 
three  quarters  of  an  acre  invaded  by  the  bugs  was  part  of  a  forty- 
acre  field  much  of  which  would  have  been  infested  and  injured  if 
this  section  had  not  been  promptly  dealt  with,  the  result  of  the 
treatment  was  much  greater  than  the  protection  of  the  corn  actually 
covered  by  it.  At  the  rate  at  which  this  treatment  was  applied  it 
would  take  two  hours  to  treat  an  acre,  or  an  average  of  five  acres 
per  day. 

At  Odin,  experiments  were  made  July  6  with  solutions  and  mix- 
tures of  various  strengths  to  test  the  effect  upon  both  insects  and 
corn.  The  plants  were  young— only  about  six  inches  high — and 
the  liquid  was  thrown  upon  them  by  hand,  care  usually  being  taken, 
however,  to  avoid  filling  the  cavity  at  the  tip  of  the  plant.  The 
emulsions  were  made  by  beating,  as  before,  the  kerosene  being 
heated  before  adding  it  to  the  soap  solution. 

Kerosene  emulsion  was  applied  in  dilutions  varying  from  four 
to  ten  per  cent,  of  kerosene,  and  whale-oil  soap  was  used  in  solutions 
varying  from  an  eighth  of  a  pound  to  two  pounds  to  the  gallon  of 
water.  With  a  four  per  cent,  kerosene  emulsion  applied  in  a  way 
to  drench  the  entire  plant  and  fill  the  cavity  within  the  terminal 
tuft  of  leaves,  no  injury  whatever  was  done  to  the  corn,  and  the 
chinch-bugs  were  nearly  all  killed.  A  similar  treatment  with  a  five 
per  cent,  emulsion,  however,  was  injurious  to  the  plants.  Some 
leaves  were  wilted  at  the  base  the  following  day,  and  seventeen 
out  of  the  thirty  plants  treated  were  finally  killed.  Still  more  serious 
injury  of  course  followed  the  use  of  the  stronger  mixtures. 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  137 

Whale-oil  soap  dissolved  by  boiling  at  the  rate  of  a  third  of  a 
pound  to  the  gallon  of  water  proved  too  weak  to  destroy  more  than 
a  comparatively  small  percentage  of  the  bugs.  With  a  half-pound 
to  the  gallon,  the  bugs  reached  by  the  liquid  were  practically  all 
destroyed,  and  none  of  the  plants  were  killed  except  where  the  ter- 
minal cavity  in  the  so-called  heart  was  filled,  in  which  case  the  con- 
centration of  the  solution  due  to  the  gradual  evaporation  of  the  fluid 
caused  the  leaves  to  wilt  and  destroyed  the  plant.  Three  quarters 
of  a  pound  to  the  gallon  was  perhaps  a  little  more  effective  as  an 
insecticide,  but  somewhat  more  dangerous  to  the  plant.  A  few 
plants  which  were  carefully  treated  were  seen  six  days  afterward 
to  have  been  injured  slightly,  the  injured  leaves  rolling  up  or  grow- 
ing in  distorted  forms.  Where  as  much  as  a  pound  and  a  half  per 
gallon  was  used  nearly  all  the  plants  were  killed,  and  two  pounds 
per  gallon  was  fatal  to  every  one. 

From  the  above  it  appears  that  a  solution  of  whale-oil  soap — one 
half  pound  to  the  gallon — is  a  safe  and  successful  insecticide  for 
corn-field  use.  As  its  cost,  however,  is  about  three  times  that  of  the 
four  per  cent,  kerosene  emulsion,  it  is  scarcely  to  be  recommended 
except  on  the  score  of  occasional  convenience.  Where  a  barrel  of 
the  four  per  cent,  emulsion  costs  thirty-four  cents,  a  barrel  of  a 
half-pound  solution  of  whale-oil  soap  will  cost  $1.12. 

Such  fluid  insecticides  may  best  be  applied  during  the  cooler  parts 
of  the  day,  since  the  plant  is  less  subject  to  injury  then  and  the  bugs 
feed  more  thoroughly.  Enough  of  the  liquid  must  be  applied  to  wet 
the  insects  thoroughly,  since  otherwise  they  are  likely  to  recover 
from  its  effects.  For  a  complete  operation,  two  and  even  three  ap- 
plications may  sometimes  be  necessary. 

EXPERIMENTS  WITH  THE  GASOLINE  BLAST-LAMP. 

The  use  of  the  ordinary  plumber's  torch,  or  some  modification 
of  it,  for  the  destruction  of  injurious  insects  on  their  food  plants 
seems  to  have  occurred  independently  to  several  persons  during  the 
last  few  years,  and  to  have  been  tried  with  some  care  as  a  practical 
measure  by  several  disinterested  men  competent  to  make  exact  ob- 
servations and  to  report  results  without  bias  or  prejudice. 

Mr.  S.  A.  McHenry,  recently  superintendent  of  one  of  the  horti- 
cultural substations  of  the  Texas  Agricultural  Experiment  Station, 
is  reported  to  have  used  it  for  several  years  against  the  harlequin 
cabbage-bug,  and  Professor  J.  M.  Stedman,  of  the  Missouri  Experi- 
ment Station,  has  also  used  it  against  the  same  insect.  Professor 
R.  H.  Pettit,  of  the  Michigan  Agricultural  College,  tried  it  on  the 


138  BULLETIN  No.  104.  [October, 

San  Jose  scale  as  far  back  as  1897,  publishing  in  the  Bulletin  of 
the  Michigan  Experiment  Station  the  earliest  report  of  an  exact 
experiment  with  it  which  I  have  seen ;  and  Professor  Craig,  of  the 
Horticultural  Department  of  Cornell  University,  has  also  tried  it 
on  this  scale.  Professor  E.  D.  Sanderson,  formerly  of  the  Texas  Ag- 
ricultural College  an^  Experiment  Station,  has  used  a  form  of  it 
on  the  cotton  boll-weevil.  Professor  Thomas  B.  Symons,  of  the 
Maryland  Agricultural  College  and  Experiment  Station,  used  it 
experimentally  on  the  San  Jose  scale,  and  on  beetles  infesting  the 
aster.  Professor  J.  L.  Phillips,  State  Entomologist  of  Virginia,  has 
also  tested  it  on  the  San  Jose  scale  with  unusual  thoroughness ;  Pro  - 
fessor  F.  M.  Webster,  Entomologist  of  the  Ohio  Agricultural  Ex- 
periment Station,  had  it  tried  four  years  ago  by  an  assistant,  Mr. 
C.  W.  Mally  (now  Government  Entomologist  in  Cape  Colony, 
South  Africa),  on  a  variety  of  insects,  including  the  chinch-bug; 
and  two  of  my  own  assistants,  Mr.  E.  S.  G.  Titus  and  Mr.  G.  I. 
Reeves,  have  used  it  on  scale  insects,  caterpillars,  and  moths ;  have 
tested  it  for  the  destruction  of  fungus  parasites  of  the  green  leaf; 
and  have  determined  its  effects  on  various  kinds  of  vegetation  when 
applied  in  a  way  to  kill  the  insect  enemies  of  the  plant.  Most  of 
these  experiments  are  unpublished,  but  their  results  have  been  gen- 
erously placed  at  my  disposal  for  use  in  this  brief  discussion. 

Although  no  one  of  those  here  mentioned  has  made  a  trial  of  the 
gasoline  torch  for  all  the  insecticide  and  fungicide  purposes  which  it 
might  possibly  serve,  the  total  results  have  a  considerable  value  as 
showing  definitely  some  things  which  can  and  some  things  which 
can  not  be  done  with  it,  and  as  indicating  the  directions  in  which 
further  trials  may  be  had  if  indeed  it  appears  that  further  trial 
is  necessary  or  worth  while.  Some  variation  and  conflict  in  the 
reports  of  some  of  these  experiments  are  evidently  due  to  differences 
in  the  apparatus  used,  this  varying  from  a  poorly  constructed  and 
feeble  torch,  made  in  Illinois  especially  for  insecticide  work,  to  a 
large  and  powerful  blast-lamp,  used  in  Texas  for  burning  the  thorns 
off  prickly  pears. 

The  idea  that  exposed  insects  of  small  size  may  be  quickly  de- 
stroyed by  the  sudden  and  brief  application  of  a  blast  of  very  hot  air, 
or  even  of  actual  flame,  without  injury  to  the  plant  on  which  they 
may  be  feeding  at  the  time,  strikes  one  favorably  at  first  thought; 
and  there  seems,  in  advance,  to  be  no  obvious  reason  why  this 
method  may  not  have  a  considerable  practical  value.  The  living 
animal  is  often  more  sensitive  to  sudden  heat  exposures  than  the 
living  plant,  and  the  margin  between  exposures  fatal  to  each  may 
in  some  cases  be  so  wide  as  to  make  this  method  fairly  safe  in 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  139 

ordinary  practice.  The  smaller  the  insect,  of  course  the  more 
quickly  it  may  be  killed  by  the  hot  blast ;  and  the  better  the  living 
tissue  of  the  plant  is  protected  by  a  lifeless  cuticle  or  a  layer  of  bark, 
the  longer  it  may  be  exposed  to  this  blast  without  being  heated  to 
the  point  of  injury.  Bark-lice  on  trees  and  shrubs  are  thus  favor- 
able objects  for  experiment;  but  where  thick-bodied  insects,  like 
caterpillars  and  large  beetles  or  bugs,  themselves  covered  with  a 
dense  crust  of  lifeless  cuticle,  are  feeding  on  the  young  green  leaf, 
the  margin  of  safety  is  greatly  narrowed  and  may  wholly  disap- 
pear. The  practical  utility  of  this  method  of  destroying  insects  in 
any  case,  evidently  depends  on  the  existence  and  extent  of  this  mar- 
gin of  safety. 

The  gasoline  blast  may,  in  fact,  be  used  to  kill  any  insect  on  any 
plant.  The  time  and  method  of  use  necessary  to  kill  the  insect  will 
vary  widely  for  different  kinds  of  insects  and  for  the  different  states 
and  stages  of  each  kind ;  and  the  time  and  method  of  use  sufficient 
to  injure  various  kinds  of  plants  will  likewise  differ  widely  accord- 
ing to  the  kinds  and  condition  of  the  plants  themselves.  The  actual 
effect  of  the  blast  on  either  insect  or  plant  will  also  vary  enormously 
according  to  small  details  of  the  method  by  which  it  is  applied. 
They  will  vary,  first,  with  variations  in  the  pressure,  which  deter- 
mines the  extent  and  heat  of  the  flame;  second,  with  the  distance 
from  the  object  at  which  the  torch  is  held ;  third,  with  the  rate  of 
movement  at  which  the  flame  is  passed  over  the  surface  treated; 
fourth,  with  the  temperature  at  the  time  and  the  amount  and  direc- 
tion of  the  wind ;  fifth,  with  the  direction  of  the  blast,  whether  per- 
pendicular or  oblique  to  the  surface;  and  sixth  (not  to  specify 
further),  with  the  steadiness  with  which  the  flame  is  applied  to  a 
given  surface,  whether  held  at  one  point  for  a  definite  time  or 
swayed  back  and  forth  over  a  considerable  surface  for  a  variable 
number  of  times. 

To  determine  the  effect  of  all  these  different  classes  of  variations 
with  sufficient  exactness  for  practical  guidance,  and  then  to  combine 
all  the  various  results  of  this  inquiry  with  each  other  in  a  way 
to  form  a  system  of  practice  which  can  be  accurately  described  and 
safely  recommended  for  general  use,  is  a  task  which  no  intelligent 
investigator  would  enter  upon  lightly,  or  without  such  preliminary 
tests  as  would  enable  him  to  judge  whether  any  important  result 
was  likely  to  come  from  more  exact  and  extensive  experiments. 
The  observations  here  reported  are  all  in  the  nature  of  such  pre- 
liminary tests,  made  by  different  persons,  each  for  his  own  satisfac- 
tion, on  different  objects  and  in  different  parts  of  the  country.  They 
are  practical  tests  rather  than  complete  scientific  experiments,  and 


140  BULLETIN  No.  104.  [October, 

their  value  is  hence  suggestive  rather  than  final.  Those  which  have 
to  do  with  the  San  Jose  scale,  the  harlequin  cabbage-bug,  and  the 
cotton  boll-weevil  are  perhaps  of  the  greatest  interest,  and  will  be 
given  first. 

The  San  Jose  Scale. — In  the  fall  of  1897,  Professor  Pettit,  of 
Michigan,  had  five  parallel  burners  fitted  to  an  ordinary  plumber's 
blast-lamp  in  such  a  way  that  a  flame  about  ten  inches  wide  could 
be  directed  against  the  surface  of  a  tree,  and  several  trials  of  this 
apparatus  were  made  during  the  following  winter  on  peach-  and 
pear-trees  badly  infested  with  the  San  Jose  scale.  "The  heat  pro- 
duced by  this  lamp,"  he  says,  "is  very  intense,  and  great  care  must 
be  observed  not  to  allow  the  flame  to  remain  at  any  one  point  long 
enough  to  injure  the  tree.  The  best  results  were  obtained  when  the 
flame  was  steadily  moved  so  that  it  covered  a  space  of  a  yard  in 
length  in  from  five  to  ten  seconds.  The  results  seemed  to  show  that 
the  blast  will  kill  the  scale-insects  with  little  or  no  injury  to  the 
tree.  The  trees  were  scorched  in  places  where  the  flame  had  moved 
too  slowly,  and  the  care  necessary  to  avoid  the  scorching  appears  to 
be  the  most  serious  drawback  to  the  use  of  the  blast  lamp.  In  care- 
less hands  much  injury  may  be  done  in  a  very  short  time,  while 
the  skilful  handling  necessary  for  success  would  be  rather  expen- 
sive under  ordinary  circumstances.  Good  judgment  must  be  exer- 
cised always,  and  the  rapidity  and  effectiveness  of  the  work  will  be 
much  modified  by  the  temperature  of  the  air,  the  direction  and  force 
of  the  wind,  the  age  of  the  trees,  and  the  thickness  of  the  incrusting 
scales."  Referring  to  these  statements  in  a  recent  letter,  Professor 
Pettit  writes  that  he  intended  that  the  lamp  should  be  used  only  in 
connection  with  a  spray,  for  burning  off  or  loosening  the  outer  lay- 
ers of  a  crust  of  scales  so  that  a  fluid  insecticide  might  penetrate  to 
those  beneath.  "I  now  realize,"  he  says,  "that  the  same  effects  may 
be  obtained  much  more  cheaply  in  other  ways." 

By  Professor  Craig,  of  Cornell  University,  a  torch  much  adver- 
tised for  the  destruction  of  insects  was  used  May  19,  1903,  against 
the  San  Jose  scale  on  the  apple,  medlar,  buffalo-berry,  and  dog-wood. 
Different  branches  were  flamed  in  various  ways  to  ascertain  the  time 
necessary  to  kill  the  scale  and  to  determine  the  minimum  exposure 
to  the  flame  of  the  torch  which  would  kill  the  cambium  layer  of  the 
tree  or  shrub.  In  respect  to  time  of  exposure  three  methods  of  treat- 
ment were  used :  passing  the  flame  so  rapidly  over  the  surface  that 
it  merely  touched  each  point  for  an  instant ;  moving  it  at  the  rate  of 
one  foot  per  second;  and  holding  it  stationary  on  the  infested  spot 
long  enough  to  count  one.  The  scales  were  reported  to  have  been 
killed  in  every  case  save  one,  in  which  a  twig  of  dogwood  had  been 


W05.\  EXPERIMENTS  ON  CORN  INSECTS.  141 

very  rapidly  flamed.  "The  general  results,"  writes  Professor  Sling- 
erland  "were  summarized  as  follows :  First,  the  torch  is  impracticable 
for  large  trees  of  apple,  plum,  pear,  peach,  or  cherry,  because  of  the 
amount  of  time  required  to  flame  the  whole  tree.  It  would  take  a 
man  several  hours  thus  to  go  over  one  large  tree ;  second,  there  is 
great  danger  of  injuring  buds  or  the  cambium  layer  on  thin-barked 
trees ;  third,  the  torch  might  be  used  on  small  nursery  stock  or  orna- 
mental shrubs  by  an  experienced  operator  who  knew  exactly  what 
time  to  expose  the  plant  to  the  flame." 

Professor  Phillips,  of  Virginia,  made  use,  against  the  San  Jose 
scale,  in  1903,  of  a  torch  sent  by  the  manufacturing  company  for 
trial  to  Professor  Alwood,  of  that  state.  "March  28,  of  this  year," 
he  says :  "I  used  this  gasoline  torch  on  two  apple-trees  four  years  of 
age. '  These  trees  were  moderately  infested  with  the  San  Jose 
scale,  and  were  treated  by  running  the  torch  over  the  surface  several 
times.  One  tree  was  exposed  to  the  torch  about  twice  as  long  as 
the  other.  This  treatment  did  not  appear  to  injure  the  trees,  neither 
did  it  kill  a  perceptible  number  of  insects. 

"I  was  not  satisfied  with  this  trial,  however,  and  detailed  a  stu- 
dent assistant,  Mr.  E.  F.  Cole,  to  test  the  torch,  which  he  did  August 
7.  The  tree  treated  was.  a  four-year-old  apple,  badly  crusted  with 
the  San  Jose  scale.  As  it  would  be  entirely  impracticable  to  use  this 
torch  against  the  San  Jose  scale  during  the  summer,  this  treatment 
was  confined  almost  entirely  to  the  trunks  and  main  branches  of  this 
tree,  but  in  treating  the  tree  in  this  manner,  of  course  a  few  of  the 
leaves  were  also  reached  by  the  flame.  The  treatment  was  so  severe 
that  the  leaves  on  the  treated  portions  of  the  tree  were  killed  at 
once,  and  when  examined  on  August  20,  portions  of  the  bast  tissues 
of  the  bark  were  found  injured  also.  Quite  a  large  number  of  scale 
insects  were  alive  at  that  date. 

"Judging  from  these  two  tests,  I  consider  that  the  use  of  this 
torch  is  quite  tedious  and  impracticable,  even  on  small  trees.  Be- 
sides, such  a  small  per  cent,  of  the  San  Jose  scales  were  destroyed 
by  it,  even  where  the  trees  were  seriously  injured  by  its  use,  that  I 
do  not  consider  it  a  practicable  remedy." 

Professor  Symons,  of  Maryland,  writes  me  that  he  personally 
conducted  some  experiments  with  the  same  kind  of  a  torch  on  dif- 
ferent varieties  of  peach  and  plum  infested  by  the  San  Jose  scale, 
but  that  the  results  were  not  at  all  satisfactory.  Although  the  insects 
were  dead  two  weeks  later  on  the  parts  which  had  been  hit  by  the 
flame,  young  scales  were  crawling  about  over  the  surface  in  con- 
siderable numbers,  showing  that  it  had  been  impossible  to  reach  all 
parts  of  the  tree,  especially  at  the  ends  of  the  branches.  If  used 


142  '  BULLETIN  No.  104.  [October, 

when  the  tree  was  in  leaf  he  could  not  avoid  burning  the  foliage.  As 
a  result  of  his  experiments,  Professor  Symons  concludes  that  it  is 
impracticable  to  control  the  San  Jose  scale  with  this  torch. 

To  these  observations  by  experts  I  may  add  a  note  of  a  trial  of 
the  torch  made  by  a  practical  gardener  on  some  infested  trees  be- 
longing to  J.  W.  Stanton,  of  Richview,  in  this  state.  By  oversight, 
these  trees  were  sprayed  with  whale-oil  soap  before  they  had  been 
critically  examined  as  to  the  final  effects  of  the  blast  on  the  San 
Jose  scale ;  but  Mr.  Stanton  writes  me  that  from  what  he  could  see 
of  the  effects  of  the  treatment  at  the  time,  he  is  of  the  opinion  that 
it  would  not  be  successful  on  tree  fruits.  One  of  my  horticultural 
inspectors,  Mr.  R.  W.  Braucher,  happened,  however,  to  examine 
one  of  these  trees  after  the  treatment  with  the  torch  and  before  the 
application  of  the  whale-oil  soap,  and  found  that  the  bark  was 
scorched  in  some  places,  and  that  in  others  the  scales  were  still 
alive. 

From  the  foregoing  experiments,  it  is  clear  that  the  gasoline 
torch  has  at  best  only  a  very  limited  application  in  the  treatment  of 
trees  infested  by  the  San  Jose  scale.  It  might  be  occasionally  used 
to  advantage,  as  suggested  by  Professor  Pettit,  to  burn  off  the  outer 
part  of  an  unusually  thick  crust  of  scales  on  the  trunk  and  largest 
branches  of  a  tree,  preliminary  to  a  treatment  with  the  lime-and- 
sulphur  wash.  As  this  insecticide  does  not  penetrate  readily  to  any 
great  depth,  it  is  sometimes  necessary  to  repeat  a  spraying  after  a 
time  if  the  tree  is  too  thickly  incrusted.  This  second  spraying  might 
perhaps  be  omitted  if  the  torch  were  first  used  on  the  crust  of  scales. 
It  would  be  the  merest  folly,  however,  to  think  of  using  it  as  a  sub- 
stitute for  an  insecticide  spray  in  the  treatment  of  the  San  Jose  scale, 
or  for  any  general  treatment  of  orchard  trees  for  any  purpose  what- 
ever. 

This  torch  was  also  tried  on  certain  other  orchard  scales  at  Ur- 
bana  during  the  fall  of  1902,  but  for  reasons  to  be  given  presently 
these  tests  are  reported  separately  farther  on. 

The  Harlequin  Cabbage-bug. — The  introduction  of  the  use 
of  the  gasoline  torch  against  the  harlequin  cabbage-bug  in  the 
South  seems  to  be  due  to  Mr.  S.  A.  McHenry,  recently  superintend- 
ent of  one  of  the  substations  of  the  Texas  Agricultural  Experiment 
Station.  Indeed,  Professor  Sanderson,  when  official  Entomologist  of 
that  state,  wrote  me  that,  so  far  as  he  knew,  Mr.  McHenry  was  the 
first  man  to  make  practical  use  of  the  blast  torch  against  insects  of 
any  kind.  He  is  said  to  have  used  it  successfully  for  several  years, 
as  have  others  in  his  section  of  the  state,  but  of  late  he  has  made 


1905.}  EXPERIMENTS  ON  CORN  INSECTS.  143 

comparatively  little  use  of  it  for  that  purpose  because  of  the  amount 
of  work  required  to  go  over  a  cabbage  plant  with  the  torch. 

Professor  J.  M.  Stedman,  of  Missouri,  writes  more  confidently 
of  its  usefulness  against  the  cabbage-bug,  saying,  under  date  of 
October  28,  1903,  "I  have  not  found  the  gasoline  torch  of  any  spe- 
cial value  as  an  insecticide  apparatus  except  in  extreme  cases  when 
one  has  a  sufficient  number  of  the  harlequin  cabbage-bugs  in  his 
cabbages  to  cause  serious  trouble.  I  have  then  used  this  torch  to 
good  advantage.  One  can  very  readily  pass  over  the  cabbages  fast 
enough  not  to  injure  them,  and  at  the  same  time  to  kill  the  harlequin 
bugs.  It  is  not  necessary  to  have  the  bugs  scorched  sufficiently  to 
drop  at  once,  as  I  have  found  that  they  will  ultimately  die  if  this 
intense  heat  has  been  very  rapidly  applied." 

This  cabbage-bug  is  not  widely  destructive  in  this  state,  although 
it  is  continuously  present  in  some  parts  of  southern  Illinois,  and  dur- 
ing one  season  extended  its  injuries  as  far  north  as  Champaign,  and 
was  once  found  in  Chicago  by  Mr.  A.  Bolter.  The  reported  effec- 
tiveness of  this  torch  against  this  insect  suggests  the  trial  of  it 
against  other  bugs,  which  cannot  be  killed  with  arsenical  poisons 
since  they  do  not  eat  the  solid  substance  of  their  food  plant  but 
merely  suck  its  sap. 

The  Cotton  Boll-weevil. — The  appearance  in  Texas  of  the  snout- 
beetle  known  as  the  Mexican  boll- weevil  has  caused  general  and  jus- 
tifiable alarm  among  the  cotton-growers  of  the  South,  and  the  former 
Texas  State  Entomologist,  Professor  Sanderson,  has  devoted  him- 
self to  an  assiduous  study  of  the  insect  and  has  made  many  experi- 
ments for  its  destruction  and  control.  This  is  indeed  the  most  im- 
portant, pressing,  and  perplexing  problem  which  the  economic  en- 
tomologist now  has  to  deal  with  in  the  Southern  States.  In  the 
course  of  his  work  against  this  insect  Profesor  Sanderson  has  tried 
two  forms  of  the  gasoline  torch;  one,  a  blast-lamp  known  as  the 
pear-burner,  used  in  southwestern  Texas -for  burning  the  thorns  off 
the  prickly  pear,  and  the  other  a  torch  sent  him  from  Illinois  by  a 
dealer  who  offers  and  advertises  it  for  sale  for  the  destruction  of  in- 
sects. The  latter  was  found  so  faulty  in  construction  that  it  could 
not  be  used,  and  it  was  consequently  returned. 

The  pear-burner,  which  generates  a  much  more  powerful  blast 
than  any  of  the  smaller  torches,  was  tried  by  Professor  Sanderson 
for  burning  up  the  squares  of  the  boll-weevil  as  they  lay  upon  the 
ground,  but  so  far,  as  he  writes  me  October  28  of  this  year,  he  has 
not  had  sufficient  success  with  it  to  indicate  that  it  has  any  value 
for  this  purpose. 


144  BULLETIN  No.  104.  [October, 

The  only  other  beetles  on  which  it  has  been  tested  by  any  of  my 
correspondents  are  certain  unspecified  species  found  on  aster  by 
Professor  Symons,  of  Maryland.  "In  this  case,"  he  says,  "it  was 
effective  in  killing  the  beetles,  but  one  has  to  be  so  extremely  careful 
not  to  hurt  the  flowers  that  I  would  hardly  recommend  it  for  prac- 
tical use." 

Experiments  at  Urbana. — In  response  to  my  request,  made 
August  5,  1902,  to  the  inventor  and  patentee  of  a  modified  form  of 
the  gasoline  torch  intended  especially  for  insecticide  work,  one  of  his 
instruments  was  sent  me  with  directions  for  its  use,  and  was  at 
once  put  into  the  hands  of  my  most  experienced  field  assistant,  Mr. 
E.  S.  G.  Titus  who,  with  the  aid  of  another  assistant,  Mr.  George  I. 
Reeves  (both  now  assistants  to  the  United  States  Entomologist), 
tried  it  at  various  times  during  the  following  two  months  on  such 
kinds  of  injurious  insects  as  could  be  found  in  any  number  at 
Urbana  at  that  time  of  the  year.  It  was  further  tried  on  a  fun- 
gus parasite  of  the  lilac  leaf,  and  on  various  kinds  of  vegetation  to 
determine  the  effect  on  the  plants  of  an  exposure  sufficient  to  kill  the 
insects  infesting  them.  Although  sent  me  expressly  for  experi- 
mental purposes,  this  instrument  proved  to  be  relatively  so  weak  in 
action  that  its  use  by  us  should  probably  be  regarded  as  a  test  of 
the  value  of  this  kind  of  a  torch  rather  than  that  of  the  torch 
method  in  general;  and  it  is  on  this  account  that  I  have  kept  our 
own  statements  separate  from  those  made  to  me  by  others,  most  of 
whom  seem  to  have  worked  with  a  more  efficient  apparatus. 

The  results  of  our  various  trials  are  here  given  as  reported  to 
me  by  Mr.  Titus  at  the  close  of  his  series  of  experiments,  about 
October  20. 

"The  torch  is  simply  an  ordinary  'plumber's  torch'  fitted  with  a 
two-gallon  gasoline  tank  and  a  three-foot  piece  of  rubber  tubing. 
A  short  iron  discharge-pipe  connects  the  rubber  tubing  with  the 
torch. 

"Filled  the  tank  about  half  full  of  gasoline  according  to  direc- 
tions. The  valve  in  this  pump  was  of  leather  and  by  no  means 
circular  in  outline,  and  it  was  at  first  rather  hard  to  secure  even 
pumping  pressure.  The  connections  were  all  very  dry  and  needed 
soaking.  After  an  hour  or  so  of  work,  cleaning  the  discharge- 
pipe  and  burner,  we  were  able  to  light  the  latter  and  get  a  flame. 

"Under  the  heaviest  pressure  obtainable — sufficient  to  force 
air  bubbles  from  the  pump  valve  and  at  the  cut-off  in  the  base  of 
the  pump — the  flame  was  tried  at  varying  distances.  At  fifteen 
inches  from  the  burner  the  heat  was  scarcely  sufficient  to  singe  the 
hair  from  the  hand,  but  a  little  closer,  ten  to  twelve  inches  distant, 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  145 

it  would  singe.  The  burner  was  used  when  running  at  full  force. 
The  effects  were  about  as  follows,  examinations  being  made  at  sev- 
eral days'  intervals : — 

"The  trunk  and  smaller  limbs  of  an  apple-tree  were  thoroughly 
treated.  This  tree  was  badly  infested  with  Forbes  and  scurfy  scales, 
and  also  had  on  it  considerable  woolly  aphis.  The  last-mentioned 
insects  were  killed  where  they  were  completely  burned  off  the  limb ; 
but  where  only  the  woolly  covering  was  burned  off,  and  the  insect 
not  actually  caused  to  drop,  there  was  little  apparent  injury.  The 
Forbes  scale  appears  not  to  have  been  injured,  except  the  young  not 
yet  old  enough  to  form  a  scale.  The  scurfy  scale  was  not  injured. 
The  smaller  limbs  were  sufficiently  treated  to  cause  the  bark  to 
blister  in  spots,  without  having  any  apparent  effect  on  mature 
scales  of  either  kind. 

"I  have  tried  the  burner  under  ordinary  pressure  at  different 
times  against  various  other  insects  and  foliage.  A  colony  of  fall 
web-worms  in  a  box-elder  tree  was  treated,  and  a  number  of  worms 
that  fell  were  placed  in  a  cage  in  the  insectary.  These  were  given 
plenty  of  fresh  food,  and  did  not  appear  to  be  inconvenienced  by 
the  lack  of  hairs  on  their  bodies.  They  grew,  and  some  of  them 
pupated.  Most  of  the  remainder  were  parasitized,  and  the  few  that 
died  were  full  grown  at  death.  The  parasites  emerged  in  due  time 
and  were  preserved. 

"Arctian  caterpillars  (woolly  bears)  treated  to  the  full  force 
of  the  burner  for  ten  to  fifteen  seconds,  or  even  longer,  had  the 
hair  thoroughly  singed  from  their  bodies,  and  some  were  blistered. 
The  majority  of  these  finished  their  growth  and  pupated.  I  could 
see  no  greater  mortality  among  them  than  ordinarily  occurs  with 
this  species  under  insectary  conditions.  Several  cabbage-worms 
were  treated  until  they  rolled  from  the  leaves.  Most  of  these  were 
not  permanently  injured,  and  those  that  died  were  burned  so  badly 
that  the  outer  skin  was  broken.  To  produce  this  effect  upon  a 
caterpillar  it  must  be  treated  with  a  direct  blaze  long  enough  to 
cause  the  leaves  to  curl  and  blacken  on  the  plants. 

"Meadow  moths  (Crambus)  flying  about  in  the  grass  were 
singed  with  the  flame.  Some  of  these  would  fly  through  the  flame 
so  close  to  the  burner  that  the  hair  on  one's  hand  would  be  quickly 
singed  off,  but  they  were  usually  uninjured  by  this  experience.  To 
kill  one  of  these  moths  it  had  to  be  followed  with  the  flame  until 
some  parts  were  burned  sufficiently  to  cause  it  to  fall,  when  it  could 
of  course  be  easily  disposed  of. 

"Lilac  leaves  badly  infested  with  mildew  were  thoroughly 
treated,  the  burner  being  held  at  varying  distances  and  acting  for 


146  BULLETIN  No.  104.  [October, 

varying  periods  of  time.  The  mildew  does  not  seem  to  have  been 
affected  where  the  leaves  were  not  injured,  and  was  rarely  affected 
where  the  leaves  were  burned  sufficiently  to  cause  them  to  curl 
and  later  to  wither.  Leaves  that  were  treated  to  the  flame  for  three 
seconds  dropped  off.  Other  leaves  treated  one  second  remained  on 
the  bush  and  were  not  perceptibly  injured.  Between  these  two  times 
(which  really  represent  flashing  the  burner  over  the  surface  and 
holding  it  there  for  an  instant)  the  leaves  show  varying  injuries.  At 
first  the  mildew  appeared  to  have  been  burned  off,  but  specimens 
which  had  been  thoroughly  treated  and  left  in  the  insectary  were 
again  covered  with  the  mildew  in  five  days. 

"Elm,  Osage  orange,  box-elder,  apple,  cherry,  plum,  grasses, 
nasturtiums,  cabbage,  pine,  cedar,  Amorpha,  walnut,  rose-bushes, 
peach,  and  several  other  trees  and  ornamental  shrubs  have  been 
treated  at  various  times!  I  find  that  when  the  flame  is  held  close 
to  the  foliage  for  a  few  seconds  this  is  visibly  injured.  If  held  a 
short  distance  away  the  injury  is  not  so  great,  but  usually  shows 
after  a  few  days  by  the  blackening  of  the  leaf  or  by  the  browning 
and  curling  of  the  edges.  Often  leaves  so  treated  will  drop  off. 

"To  sum  up:  The  use  of  sufficient  heat  to  destroy  effectually 
insect  larvae  of  the  kinds  we  treated,  will  injure  the  foliage  and  often 
the  twigs." 

Mention  may  be  made  of  a  trial  of  the  torch  by  Mr.  Mally,  in 
Ohio  in  1898,  the  details  of  which  can  not  now  be  given  because 
the  record  is  not  accessible.  This  torch,  obtained  from  Illinois,  was 
put  into  Mr.  Mally's  hands  by  Professor  F.  M.  Webster,  with  in- 
structions to  give  it  a  thorough  test.  It  was  taken  by  Mr.  Mally 
on  one  of  his  field  trips,  used  on  a  variety  of  insects,  including  the 
chinch-bug,  and  returned  with  the  general  report  that  it  was  un- 
satisfactory for  its  purpose. 

USE  OF  THE  GASOLINE  TORCH  AGAINST  THE  CHINCH-BUG. 

Notwithstanding  the  generally  unfavorable  character  of  the 
statements  made  to  me  concerning  this  torch  by  those  best  able  to 
judge  of  its  value,  it  seems  that  it  may  have  a  field  of  usefulness 
for  the  destruction  of  certain  kinds  of  injurious  insects.  Thinking 
that  it  might  profitably  be  tried  in  comparison  with  other  aids  to 
the  trap  and  barrier  method  for  the  destruction  of  chinch-bugs  as 
they  come  out  of  small  grain  in  midsummer,  I  provided  for  a  series 
of  field  trials  with  a  first-class  torch,  in  connection  with  other  experi- 
ments on  the  chinch-bug  made  during  the  summer  of  1904.  To 
make  sure  of  having  a  good  example  of  this  form  of  blast-lamp,  one 


1905.}  EXPERIMENTS  ON  CORN  INSECTS.  147 

was  bought  from  the  manufacturer  in  person,  who  was  kind  enough 
to  give  careful  instructions  and  to  illustrate  personally  its  use  in  the 
field. 

Two  miles  south  of  Carbondale  was  a  field  of  forty  acres  of  corn 
adjoining  wheat  infested  by  chinch-bugs,  which  had  almost  com- 
pletely destroyed  the  corn  on  an  area  two  hundred  and  twenty  yards 
long  and  seventy  yards  in  depth.  Only  a  few  scattering  hills  re- 
mained on  this  strip,  and  a  good  deal  of  this  was  lying  almost  flat 
on  the  ground.  Farther  within  the  field  the  corn  was  only  moder- 
ately infested,  but  was  of  course  still  liable  to  serious  injury  by  the 
invading  host.  July  30,  when  this  experiment  began,  most  of  the 
bugs  had  developed  wings,  though  many  were  still  to  be  found  in 
all  stages  from  the  very  young  to  the  lately  transformed  adult. 

The  lamp  was  first  used  on  fallen  hills  thickly  covered  with  the 
bugs,  many  of  which,  however,  were  concealed  within  leaves  closely 
rolled  for  their  entire  length.  When  the  blast  of  flame  was  turned 
upon  the  corn,  many  bugs  exposed  on  the  surface  of  the  plants  fell  to 
the  ground,  where  they  could  easily  be  killed  by  following  them  with 
the  flame.  Many  others,  however,  would  not  leave  their  shelter 
among  the  leaves,  and  these  were  left  uninjured. 

Where  the  field  was  only  moderately  infested,  scattered  adults 
and  clusters  of  them  exposed  to  the  flame  dropped  to  the  ground 
at  once,  where  they  could  be  quickly  destroyed ;  but  many  dropped 
from  the  side  of  the  hill  farthest  from  the  torch,  where  they  could 
not  be  reached  until  the  operator  returned  down  the  other  side  of 
the  row,  as  only  one  side  of  the  hill  could  be  treated  at  once.  Indeed, 
for  a  satisfactory  application  of  this  method  it  would  be  necessary 
that  two  men  should  take  a  row  together,  one  on  each  side,  operat- 
ing against  each  hill  simultaneously.  Even  this  would  not  wholly 
prevent  the  premature  escape  of  the  bugs,  as  many  fell  from  the 
corn  two  or  three  hills  in  advance  of  the  roaring  blast  and  hurried 
away  in  an  effort  to  escape.  Those  which  remained  secreted  behind 
the  ensheathing  bases  of  the  leaves  were  also,  of  course,  protected 
from  injury.  In  this  respect  the  blast-lamp  proved  less  efficient  than 
the  kerosene  emulsion,  since  the  latter  was  especially  useful  in 
reaching  the  accumulations  of  chinch-bugs  hidden  behind  the  leaves. 

For  a  more  accurate  test  of  the  effect  of  the  hot  blast  ten  cages 
were  arranged  in  such  a  way  that  the  bugs  could  be  treated  within 
them  and  held  captive  under  normal  conditions  for  observation  after- 
wards. In  one  of  these  cages  two  hundred  and  fifty  chinch-bugs, 
mainly  adults,  were  flamed  with  the  exit  of  the  blast  held  for  one 
second  an  inch  from  the  bugs,  the  pressure  having  been  pumped  up 
about  to  a  maximum  by  two  hundred  strokes  of  the  piston.  The 


148  BULLETIN  No.  104.  [October, 

following  day  eighty  per  cent,  of  the  bugs  were  dead,  together  with 
several  adult  blister-beetles  (Epicauta  marginata)  and  Colorado  po- 
tato-beetles treated  at  the  same  time. 

In  another  test  like  the  preceding,  except  that  the  bugs  were  ex- 
posed to  the  blast  for  two  seconds,  eighty  per  cent,  were  dead  the 
following  day.  A  third  experiment  duplicated  the  first  with  a  result 
to  kill  eighty-five  per  cent,  of  the  bugs.  In  a  fourth  cage  the  flame 
was  held  for  a  second  two  inches  from  the  bugs,  and  the  following 
day  seventy-five  per  cent,  of  the  two  hundred  and  fifty  treated  were 
found  to  have  been  killed.  At  a  distance  of  four  inches  the  flame 
killed  but  ten  per  cent.,  the  remainder  crawling  about,  apparently 
uninjured,  twenty-four  hours  later.  An  adult  potato-beetle  and  two 
larvae  of  the  same,  a  common  cabbage-worm,  and  a  caterpillar  of 
the  cabbage  Plusia  were  likewise  uninjured  by  this  treatment.  In 
another  experiment  it  was  shown  that  if  the  burner  were  held  three 
seconds  at  a  distance  of  four  inches  from  the  insects,  only  ten  per 
cent,  of  the  chinch-bugs  were  killed. 

A  thousand  chinch-bugs  were  next  exposed  to  a  gentle  blast  of 
the  gasoline  flame  until  they  were  all  unable  to  crawl.  On  the  fol- 
lowing day  about  fifty  of  them  were  still  able  to  move,  although  the 
legs  and  other  appendages  of  some  of  these  were  scorched. 

In  order  to  ascertain  whether  the  bugs  might  die  from  the  after- 
effects of  the  blast,  a  thousand  specimens  in  another  cage  were  sub- 
jected to  an  extreme  scorching  heat  without  killing  them  at  the  time. 
On  the  following  day  at  least  half  of  them  crawled  away,  evidently 
uninjured.  Another  lot  of  a<  thousand  were  flamed  until  a  third 
were  killed  outright,  the  remainder  being  rapidly  flamed  several 
times  but  left  able  to  crawl  away.  On  the  following  day  at  least 
two  thirds  of  the  bugs  were  alive.  From  these  experiments  it  ap- 
pears that  bugs  not  killed  at  the  time  of  treatment  do  not  ordinarily 
die  thereafter.  A  lot  of  two  thousand  chinch-bugs  or  more,  col- 
lected from  corn  and  confined  in  a  similar  cage,  which  were  kept  as 
a  check  during  the  course  of  these  experiments,  lived  with  less  than 
one  per  cent,  of  loss,  and  these  were  probably  injured  in  collecting. 

To  determine  the  resisting  power  of  the  corn  to  the  hot  blast 
of  the  gasoline  torch  several  plats,  equally  infested  and  all  in  one 
field,  were  treated  variously.  The  flame  was  moved  over  the  plants 
sometimes  quickly,  sometimes  slowly,  and  was  sometimes  held 
close  to  the  leaves,  sometimes  at  a  greater  distance.  In  this  experi- 
ment the  unit  was  a  plat  of  a  hundred  hills  of  corn,  which  averaged 
three  feet  high  at  the  time.  All  plats  were  treated  in  the  afternoon 
of  July  30,  the  weather  being  clear  and  hot,  with  a  little  wind.  The 
lamp  was  used  at  a  high  pressure,  produced  by  two  hundred  sue- 


1905.}  EXPERIMENTS  ON  CORN  INSECTS.  149 

cessive  strokes  of  the  pump.  The  heat  was  sufficient  to  scorch  the 
hairs  from  the  back  of  the  hand  at  twelve  inches  from  the  burner, 
and  to  burn  in  two  in  thirty  seconds  a  stalk  of  corn  held  four  inches 
from  the  nozzle. 

In  the  first  plat  the  flame  was  passed  steadily  upward  for  a  foot 
along  the  stalk  at  the  rate  of  about  two  feet  per  second,  this  flaming 
process  being  four  times  repeated  for  each  side  of  the  hill  with  the 
nozzle  held  an  inch  or  less  from  the  plant.  Each  plant  was  thus 
exposed  to  the  blast  for  four  seconds  in  all,  a  half  a  second  each 
time.  Two  days  later  some  of  the  bugs  were  dead,  but  many  were 
still  alive,  and  many  stalks  of  corn  were  seriously  injured,  scarcely 
a  hill  in  the  plat  having  wholly  escaped  scorching.  In  some  hills 
the  large  leaves  were  burned,  and  in  nearly  all  the  lowest  leaves  were 
visibly  scorched. 

This  experiment  was  repeated  on  another  plat  except  that  the 
tube  was  held  about  four  inches  from  the  plants.  Two  days  later 
the  corn  was  less  injured  than  in  plat  one,  but  nearly  all  was  scorched 
more  or  less,  especially  the  upper  leaves.  Some  of  the  bugs  were 
still  alive,  probably  those  which  fell  to  the  ground  and  escaped  and 
those  secluded  beneath  the  sheaths  of  the  leaves. 

In  another  plat  the  treatment  was  varied  by  flaming  the  bugs 
at  the  base  of  the  plant  as  they  fell  upon  the  ground,  using  on  an 
average  two  seconds  additional  for  each  hill.  The  torch  was  handled 
about  as  in  the  first  experiment,  and  the  plants  were  similarly  in- 
jured. The  hardened  cuticle  at  the  base  of  the  stalk  was  less  likely 
to  be  scorched  than  the  green  and  tender  leaves.  The  bugs  were 
nearly  all  destroyed  on  this  plant,  although  a  few  were  still  alive  the 
following  day. 

By  other  experiments  it  was  found  that  by  two  or  three  treat- 
ments, separated  by  intervals  sufficient  to  allow  the  escaping  bugs 
to  collect  again,  the  corn  might  be  almost  completely  cleared  of 
bugs,  but,  unfortunately,  without  the  most  painstaking  care  injury 
to  the  plants  was  such  as  to  make  this  form  of  treatment  quite  in- 
admissible. 

The  cost  of  these  operations  was  considerably  less  than  the  cor- 
responding treatment  with  kerosene  emulsion.  The  time  required 
was  practically  the  same,  but  the  cost  per  acre  was  thirty-four  cents 
for  the  emulsion  and  fifteen  cents  for  the  gasoline. 

It  was  Mr.  Taylor's  judgment  that  two  treatments  with  a  four 
per  cent,  emulsion  would  have  about  the  same  effect  upon  the  bugs 
as  three  applications  of  the  torch,  but  the  latter  is  more  convenient 
to  use,  requiring  no  previous  preparation  of  the  fluid  and  no  hauling 
of  water  to  the  field.  The  risk  of  injury  to  the  corn  is  of  course 


150  BULLETIN  No.  104.  [October, 

much  greater  with  the  torch — especially  in  the  hands  of  unskilled  or 
careless  workmen.  The  price  of  $10  charged  for  the  blast-lamp 
would  determine  the  choice  of  many,  since  apparatus  may  be  wholly 
dispensed  with  in  the  preparation  and  application  of  the  kerosene 
emulsion. 

There  is  an  evident  use  for  the  gasoline  torch  in  the  destruc- 
tion of  bugs  collecting  either  in  the  dusty  furrow  or  along  the  coal- 
tar  line,  where  these  are  used  as  barriers  against  the  movement  of 
the  chinch-bugs  from  small  grain  to  corn.  By  directing  the  hot 
blast  against  the  insects  trapped  in  the  furrow  or  collecting  along 
the  tar  line  on  the  ground,  these  could  be  rapidly  killed  at  small 
expense,  and  the  post-hole  traps  might  thus  be  dispensed  with. 
Care  would  be  necessary,  however,  to  prevent  the  burning  or  drying 
of  the  tar  by  the  flame. 

It  also  seems  quite  probable  that  a  fine  spray  of  pure  kerosene, 
or  even  of  crude  petroleum,  might  be  used  to  good  advantage  for  the 
destruction  of  the  chinch-bugs  on  the  ground,  and  perhaps  at  less 
expense.  On  the  coal-tar  line  the  kerosene  might  be  preferred  be- 
cause it  would  tend  to  soften  the  tar  and  lengthen  the  period  of  its 
efficiency  as  a  barrier,  and  could  not  dry  and  harden  it  as  would  the 
flame.  Opportunity  was  wanting  last  season  for  experiment  cover- 
ing these  last  suggested  points,  and  they  must  consequently  be  tested 
at  some  other  time. 

At  a  later  date  the  blast-lamp  was  used  in  the  potato  field  to  de- 
stroy the  adults  and  larvae  of  the  common  potato-beetle.  For  this 
operation  it  was  found  entirely  impracticable.  The  insects  could 
of  course  be  killed,  but  at  an  expense  of  about  fifteen  hours  of  labor 
per  acre. 

GENERAL,  SUMMARY. 

These  experiments  may  be  considered  as  a  test  of  the  efficiency 
of  barriers  constructed  to  arrest  the  movement  of  chinch-bugs  in 
passing  from  small  grain  to  corn  at  harvest-time,  under  conditions 
unfavorable  to  success,  that  is,  when  the  chinch-bugs  were  not  so 
numerous  as  rapidly  to  destroy  the  wheat — compelling  their  migra- 
tion en  masse — and  when  the  weather  was  neither  extremely  hot 
nor  very  dry.  The  spring  and  early  summer  of  1904  proved  to  be 
unusually  wet,  and  chinch-bugs  consequently  were  not  generally 
abundant  enough  to  threaten  any  great  injury  to  corn.  The  weather 
also  prevented  the  use  of  the  dusty  furrow,  most  commonly  resorted 
to  as  a  barrier  to  the  movements  of  chinch-bugs,  and  compelled  a 
reliance  on  the  coal-tar  line  with  post-hole  traps  instead.  So  far  as 
the  season  permitted  a  real  test  of  the  operation,  it  was  completely 


1905.]  EXPERIMENTS  ON  CORN  INSECTS.  151 

effective  for  the  protection  of  corn,  and  there  is  no  doubt  that  it 
would  have  been  equally  so  if  chinch-bugs  had  been  ten  or  a  hun- 
dred times  as  numerous. 

A  partial  failure  of  the  experiment  due  to  the  character  of  the 
weather  of  the  season  did  not  diminish  its  value  as  a  means  of  de- 
termining- the  cost  of  an  effective  operation  on  the  scale  of  actual 
farm  practice.  It  was  demonstrated  that  the  coal-tar  strip  may  be 
laid  down  and  maintained  for  four  weeks — the  maximum  period 
necessary — at  a  cost  of  $22  a  mile,  with  the  effect  to  trap  all  bugs 
approaching  the  line,  where  they  may  be  readily  and  rapidly  killed. 
The  average  cost  of  making  a  dusty  furrow  or  ditch  sufficient  to  ar- 
rest and  trap  all  chinch-bugs  attempting  to  cross  it  .was  approxi- 
mately three  cents  a  rod,  or  $10  a  mile,  for  labor  only,  no  materials 
being  required.  This  furrow  can  not  be  used,  however,  except  in 
dry  hot  weather. 

Various  methods  of  preparing  the  ground  for  the  coal-tar  line 
were  used  in  comparison.  One  of  the  most  satisfactory  methods  was 
that  of  plowing  a  back  furrow  in  the  stubble  near  the  edge  of  the 
field,  and  packing  this  with  a  roller  or  beating  it  flat  and  hard  with 
spades.  A  strip  of  sod  may  be  prepared  to  receive  the  line  by  scrap- 
ing away  the  grassy  surface  with  an  ordinary  farm  scraper,  after- 
wards leveling  and  smoothing  it  carefully  with  a  shovel  or  hoe. 

A  kerosene  emulsion  prepared  by  mixing  two  parts  of  kerosene 
and  one  of  soap-suds  by  violently  beating  with  a  stick  for  about  five 
minutes,  and  diluting  to  contain  four  per  cent,  of  kerosene,  was  found 
efficient  for  the  destruction  of  all  the  chinch-bugs  touched  by  it,  and 
was  successfully  used  for  clearing  rows  of  corn  along  the  borders 
of  a  field  which  had  become  infested  for  lack  of  "effective  barriers. 
Stronger  kerosene  mixtures  made  in  this  way  commonly  proved  in- 
jurious to  the  plant.  A  barrel  of  diluted  emulsion  costs  about  thirty- 
four  cents.  It  was  applied  to  the  corn  by  hand  at  an  average  rate 
of  a  barrel  an  acre — five  acres  per  day  for  each  man.  A  solution 
of  whale-oil  soap,,  one  half  pound  to  the  gallon  of  water,  proved  to 
be  a  safe  and  sufficient  insecticide  for  corn-field  use.  Its  cost  was 
$1.12  a  barrel. 

The  gasoline  blast-lamp,  tested  on  a  great  variety  of  insects, 
was  found  to  be  only  occasionally  useful.  By  two  or  three  suc- 
cessive treatments  separated  by  intervals  sufficient  to  allow  the 
chinch-bugs  which  escape  to  collect  upon  the  plant,  badly  infested 
corn  might  be  almost  completely  cleared  of  bugs,  but  serious  injury 
to  the  corn  itself  was  almost  certain  unless  the  most  painstaking  care 
was  used.  The  cost  of  material  is  less  than  that  of  kerosene,  amount- 
ing to  only  about  fifteen  cents  an  acre  for  each  treatment  with  the 


152  BULLETIN  No.  104.  [October, 

former  and  thirty-four  cents  for  the  latter.  Three  applications 
with  the  torch  were  about  equal  to  two  treatments  with  the  kero- 
sene emulsion,  the  first  being  most  convenient  to  use  but  also  most 
dangerous  to  the  plant.  It  is  suggested  that  this  gasoline  torch  may 
be  found  a  convenient  apparatus  for  destroying  chinch-bugs  collect- 
ing either  in  the  dusty  furrow  or  along  the  coal-tar  line,  when  these 
are  used  as  barriers. 


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